(ℓ, k)-regular partitions
DefinitionNumber of \((\ell, k)\)-regular partitions#✓fully proved
For natural numbers \(\ell\), \(k\) and \(n\), \(b_{\ell,k}(n)\) is the number of \((\ell, k)\)-regular partitions of \(n\), that is, partitions of \(n\) none of whose parts is divisible by \(\ell\) or by \(k\).
public def regularPartitionCount (l k n : ℕ) : ℕ :=
((Finset.univ : Finset n.Partition).filter fun p => ∀ i ∈ p.parts, ¬ l ∣ i ∧ ¬ k ∣ i).card
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Section 1 (definition ofb_{ℓ,k}(n)).
Used by 9
TheoremThe \((4, 9)\)-regular partition count at zero#✓fully proved
The number \(b_{4,9}(0)\) of \((4, 9)\)-regular partitions of \(0\), that is, partitions of \(0\) none of whose parts is divisible by \(4\) or by \(9\), equals \(1\): the only such partition is the empty partition.
public theorem regularPartitionCount_four_nine_zero : regularPartitionCount 4 9 0 = 1
public def regularPartitionCount (l k n : ℕ) : ℕ :=
((Finset.univ : Finset n.Partition).filter fun p => ∀ i ∈ p.parts, ¬ l ∣ i ∧ ¬ k ∣ i).card
WantedExt/Combinatorics/Enumerative/Partition/RegularPartitionsLKWanted.lean:41
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Section 1 (definition ofb_{ℓ,k}(n)).
Uses 1
TheoremFor small \(n\) every partition is \((\ell, k)\)-regular#✓fully proved
Let \(\ell\), \(k\) and \(n\) be natural numbers with \(n < \ell\) and \(n < k\), and write \(b_{\ell,k}(n)\) for the number of \((\ell, k)\)-regular partitions of \(n\) (partitions none of whose parts is divisible by \(\ell\) or by \(k\)) and \(p(n)\) for the number of all partitions of \(n\). Then every partition of \(n\) is \((\ell, k)\)-regular, so \(b_{\ell,k}(n) = p(n)\).
public theorem regularPartitionCount_of_lt {l k n : ℕ} (hl : n < l) (hk : n < k) :
regularPartitionCount l k n = Fintype.card n.Partition
public def regularPartitionCount (l k n : ℕ) : ℕ :=
((Finset.univ : Finset n.Partition).filter fun p => ∀ i ∈ p.parts, ¬ l ∣ i ∧ ¬ k ∣ i).card
WantedExt/Combinatorics/Enumerative/Partition/RegularPartitionsLKWanted.lean:41
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Section 1 (definition ofb_{ℓ,k}(n)).
Uses 1
TheoremParity of \((4, p)\)-regular partitions in nonresidue progressions#●ready to prove
Let \(p \ge 5\) be a prime and let \(r\) be a natural number such that \(8r + 1\) is not a square modulo \(p\) (a quadratic nonresidue). Write \(b_{4,p}(m)\) for the number of \((4, p)\)-regular partitions of \(m\), that is, partitions of \(m\) none of whose parts is divisible by \(4\) or by \(p\). Then \(b_{4,p}(pn + r) \equiv 0 \pmod 2\) for every natural number \(n\).
Restricting \(r\) to natural numbers loses nothing: every residue class modulo \(p\) has a natural-number representative.
public theorem_wanted regularPartitionCount_four_prime_mod_two {p r : ℕ} (hp : p.Prime)
(h5 : 5 ≤ p) (hr : ¬ IsSquare ((8 * r + 1 : ℕ) : ZMod p)) (n : ℕ) :
regularPartitionCount 4 p (p * n + r) ≡ 0 [MOD 2]
public def regularPartitionCount (l k n : ℕ) : ℕ :=
((Finset.univ : Finset n.Partition).filter fun p => ∀ i ∈ p.parts, ¬ l ∣ i ∧ ¬ k ∣ i).card
WantedExt/Combinatorics/Enumerative/Partition/RegularPartitionsLKWanted.lean:41
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Theorem 1 (jis-2025-25.6.1-thm-1).
Uses 1
TheoremParity of \((2, p)\)-regular partitions in nonresidue progressions#●ready to prove
Let \(p \ge 5\) be a prime and let \(r\) be a natural number such that \(24r + 1\) is not a square modulo \(p\) (a quadratic nonresidue). Write \(b_{2,p}(m)\) for the number of \((2, p)\)-regular partitions of \(m\), that is, partitions of \(m\) none of whose parts is divisible by \(2\) or by \(p\). Then \(b_{2,p}(pn + r) \equiv 0 \pmod 2\) for every natural number \(n\).
public theorem_wanted regularPartitionCount_two_prime_mod_two {p r : ℕ} (hp : p.Prime)
(h5 : 5 ≤ p) (hr : ¬ IsSquare ((24 * r + 1 : ℕ) : ZMod p)) (n : ℕ) :
regularPartitionCount 2 p (p * n + r) ≡ 0 [MOD 2]
public def regularPartitionCount (l k n : ℕ) : ℕ :=
((Finset.univ : Finset n.Partition).filter fun p => ∀ i ∈ p.parts, ¬ l ∣ i ∧ ¬ k ∣ i).card
WantedExt/Combinatorics/Enumerative/Partition/RegularPartitionsLKWanted.lean:41
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Theorem 2 (jis-2025-25.6.1-thm-2).
Uses 1
TheoremCongruences modulo \(12\) for \(b_{4,9}\) along powers of \(2\)#●ready to prove
Let \(b_{4,9}(n)\) be the number of partitions of \(n\) with no part divisible by \(4\) or by \(9\). For all natural numbers \(\alpha \ge 3\) and \(n\), \(b_{4,9}(2^\alpha n + 6 \cdot 2^{\alpha - 3} + 1) \equiv 0 \pmod{12}\).
public theorem_wanted regularPartitionCount_four_nine_mod_twelve {α : ℕ} (hα : 3 ≤ α) (n : ℕ) :
regularPartitionCount 4 9 (2 ^ α * n + 6 * 2 ^ (α - 3) + 1) ≡ 0 [MOD 12]
public def regularPartitionCount (l k n : ℕ) : ℕ :=
((Finset.univ : Finset n.Partition).filter fun p => ∀ i ∈ p.parts, ¬ l ∣ i ∧ ¬ k ∣ i).card
WantedExt/Combinatorics/Enumerative/Partition/RegularPartitionsLKWanted.lean:41
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Theorem 3 (jis-2025-25.6.1-thm-3).
Uses 1
TheoremThe 2-dissection of \(f_9/f_1\)#●ready to prove
Write \(f_k = (q^k; q^k)_\infty\) for the Euler products. In the ring of integer power series in \(q\),
Since each \(f_k\) with \(k \ge 1\) has constant term \(1\) and is therefore invertible, this is the identity \(f_9 / f_1 = f_{12}^3 f_{18} / (f_2^2 f_6 f_{36}) + q f_4^2 f_6 f_{36} / (f_2^3 f_{12})\) with both sides multiplied by \(f_1 f_2^3 f_6 f_{12} f_{36}\).
public theorem_wanted f9_div_f1_two_dissection :
𝔣 9 * 𝔣 2 ^ 3 * 𝔣 6 * 𝔣 12 * 𝔣 36 =
𝔣 1 * 𝔣 2 * 𝔣 12 ^ 4 * 𝔣 18 + X * 𝔣 1 * 𝔣 4 ^ 2 * 𝔣 6 ^ 2 * 𝔣 36 ^ 2
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Lemma 7 (jis-2025-25.6.1-lem-7).
Uses 1
TheoremThe 2-dissection of \(f_3/f_1^3\)#●ready to prove
Write \(f_k = (q^k; q^k)_\infty\) for the Euler products. In the ring of integer power series in \(q\),
Since each \(f_k\) with \(k \ge 1\) has constant term \(1\) and is therefore invertible, this is the identity \(f_3 / f_1^3 = f_4^6 f_6^3 / (f_2^9 f_{12}^2) + 3q f_4^2 f_6 f_{12}^2 / f_2^7\) with both sides multiplied by \(f_1^3 f_2^9 f_{12}^2\).
public theorem_wanted f3_div_f1_cube_two_dissection :
𝔣 3 * 𝔣 2 ^ 9 * 𝔣 12 ^ 2 =
𝔣 1 ^ 3 * 𝔣 4 ^ 6 * 𝔣 6 ^ 3 + 3 * X * 𝔣 1 ^ 3 * 𝔣 2 ^ 2 * 𝔣 4 ^ 2 * 𝔣 6 * 𝔣 12 ^ 4
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Lemma 8 (jis-2025-25.6.1-lem-8).
Uses 1
TheoremThe 2-dissection of \(f_3^2/f_1^2\)#●ready to prove
Write \(f_k = (q^k; q^k)_\infty\) for the Euler products. In the ring of integer power series in \(q\),
Since each \(f_k\) with \(k \ge 1\) has constant term \(1\) and is therefore invertible, this is the identity \(f_3^2 / f_1^2 = f_4^4 f_6 f_{12}^2 / (f_2^5 f_8 f_{24}) + 2q f_4 f_6^2 f_8 f_{24} / (f_2^4 f_{12})\) with both sides multiplied by \(f_1^2 f_2^5 f_8 f_{12} f_{24}\).
public theorem_wanted f3_sq_div_f1_sq_two_dissection :
𝔣 3 ^ 2 * 𝔣 2 ^ 5 * 𝔣 8 * 𝔣 12 * 𝔣 24 =
𝔣 1 ^ 2 * 𝔣 4 ^ 4 * 𝔣 6 * 𝔣 12 ^ 3 +
2 * X * 𝔣 1 ^ 2 * 𝔣 2 * 𝔣 4 * 𝔣 6 ^ 2 * 𝔣 8 ^ 2 * 𝔣 24 ^ 2
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Lemma 9 (jis-2025-25.6.1-lem-9).
Uses 1
TheoremThe 2-dissections of \(1/f_1^4\), \(1/f_1^8\) and \(1/f_1^{12}\)#●ready to prove
Write \(f_k = (q^k; q^k)_\infty\) for the Euler products. In the ring of integer power series in \(q\), the following three identities hold:
Since each \(f_k\) with \(k \ge 1\) has constant term \(1\) and is therefore invertible, dividing by \(f_1^4 f_2^{14} f_8^4\), \(f_1^8 f_2^{28} f_8^8\) and \(f_1^{12} f_2^{42} f_8^{12}\) respectively turns these into the 2-dissections \(1/f_1^4 = f_4^{14}/(f_2^{14} f_8^4) + 4q f_4^2 f_8^4/f_2^{10}\), \(1/f_1^8 = f_4^{28}/(f_2^{28} f_8^8) + 8q f_4^{16}/f_2^{24} + 16q^2 f_4^4 f_8^8/f_2^{20}\) and \(1/f_1^{12} = f_4^{42}/(f_2^{42} f_8^{12}) + 12q f_4^{30}/(f_2^{38} f_8^4) + 48q^2 f_4^{18} f_8^4/f_2^{34} + 64q^3 f_4^6 f_8^{12}/f_2^{30}\).
public theorem_wanted one_div_f1_pow_four_eight_twelve_two_dissection :
𝔣 2 ^ 14 * 𝔣 8 ^ 4 = 𝔣 1 ^ 4 * 𝔣 4 ^ 14 + 4 * X * 𝔣 1 ^ 4 * 𝔣 2 ^ 4 * 𝔣 4 ^ 2 * 𝔣 8 ^ 8 ∧
𝔣 2 ^ 28 * 𝔣 8 ^ 8 =
𝔣 1 ^ 8 * 𝔣 4 ^ 28 + 8 * X * 𝔣 1 ^ 8 * 𝔣 2 ^ 4 * 𝔣 4 ^ 16 * 𝔣 8 ^ 8 +
16 * X ^ 2 * 𝔣 1 ^ 8 * 𝔣 2 ^ 8 * 𝔣 4 ^ 4 * 𝔣 8 ^ 16 ∧
𝔣 2 ^ 42 * 𝔣 8 ^ 12 =
𝔣 1 ^ 12 * 𝔣 4 ^ 42 + 12 * X * 𝔣 1 ^ 12 * 𝔣 2 ^ 4 * 𝔣 4 ^ 30 * 𝔣 8 ^ 8 +
48 * X ^ 2 * 𝔣 1 ^ 12 * 𝔣 2 ^ 8 * 𝔣 4 ^ 18 * 𝔣 8 ^ 16 +
64 * X ^ 3 * 𝔣 1 ^ 12 * 𝔣 2 ^ 12 * 𝔣 4 ^ 6 * 𝔣 8 ^ 24
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Lemma 10 (jis-2025-25.6.1-lem-10).
Uses 1
TheoremThe 2-dissection of \(1/(f_1 f_3)\)#●ready to prove
Write \(f_k = (q^k; q^k)_\infty\) for the Euler products. In the ring of integer power series in \(q\),
Since each \(f_k\) with \(k \ge 1\) has constant term \(1\) and is therefore invertible, this is the identity \(1 / (f_1 f_3) = f_8^2 f_{12}^5 / (f_2^2 f_4 f_6^4 f_{24}^2) + q f_4^5 f_{24}^2 / (f_2^4 f_6^2 f_8^2 f_{12})\) with both sides multiplied by \(f_1 f_3 f_2^4 f_4 f_6^4 f_8^2 f_{12} f_{24}^2\).
public theorem_wanted one_div_f1_f3_two_dissection :
𝔣 2 ^ 4 * 𝔣 4 * 𝔣 6 ^ 4 * 𝔣 8 ^ 2 * 𝔣 12 * 𝔣 24 ^ 2 =
𝔣 1 * 𝔣 3 * 𝔣 2 ^ 2 * 𝔣 8 ^ 4 * 𝔣 12 ^ 6 +
X * 𝔣 1 * 𝔣 3 * 𝔣 4 ^ 6 * 𝔣 6 ^ 2 * 𝔣 24 ^ 4
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Lemma 11 (jis-2025-25.6.1-lem-11).
Uses 1
TheoremGenerating function of \(b_{4,9}\) at odd arguments#●ready to prove
Let \(b_{4,9}(n)\) be the number of partitions of \(n\) with no part divisible by \(4\) or by \(9\), and write \(f_k = (q^k; q^k)_\infty\) for the Euler products. In the ring of integer power series in \(q\),
Since \(f_1\) and \(f_6\) have constant term \(1\) and are therefore invertible, this says \(\sum_{n \ge 0} b_{4,9}(2n + 1) q^n = f_2^3 f_3 / (f_1^3 f_6)\).
public theorem_wanted regularPartitionCount_four_nine_odd_generatingFunction :
𝔣 1 ^ 3 * 𝔣 6 * PowerSeries.mk (fun n => (regularPartitionCount 4 9 (2 * n + 1) : ℤ)) =
𝔣 2 ^ 3 * 𝔣 3
public def regularPartitionCount (l k n : ℕ) : ℕ :=
((Finset.univ : Finset n.Partition).filter fun p => ∀ i ∈ p.parts, ¬ l ∣ i ∧ ¬ k ∣ i).card
WantedExt/Combinatorics/Enumerative/Partition/RegularPartitionsLKWanted.lean:41
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Theorem 12 (jis-2025-25.6.1-thm-12).
Uses 2
TheoremAn internal congruence modulo \(4\) for \(b_{4,9}\)#●ready to prove
Let \(b_{4,9}(n)\) be the number of partitions of \(n\) with no part divisible by \(4\) or by \(9\). For every natural number \(n\), \(b_{4,9}(16n + 1) \equiv b_{4,9}(4n + 1) \pmod 4\).
public theorem_wanted regularPartitionCount_four_nine_internal_mod_four (n : ℕ) :
regularPartitionCount 4 9 (16 * n + 1) ≡ regularPartitionCount 4 9 (4 * n + 1) [MOD 4]
public def regularPartitionCount (l k n : ℕ) : ℕ :=
((Finset.univ : Finset n.Partition).filter fun p => ∀ i ∈ p.parts, ¬ l ∣ i ∧ ¬ k ∣ i).card
WantedExt/Combinatorics/Enumerative/Partition/RegularPartitionsLKWanted.lean:41
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Theorem 13 (jis-2025-25.6.1-thm-13).
Uses 1
Theorem\(b_{4,9}(16n + 13)\) is divisible by \(4\)#●ready to prove
Let \(b_{4,9}(n)\) be the number of partitions of \(n\) with no part divisible by \(4\) or by \(9\). For every natural number \(n\), \(b_{4,9}(16n + 13) \equiv 0 \pmod 4\).
public theorem_wanted regularPartitionCount_four_nine_sixteen_mul_add_thirteen (n : ℕ) :
regularPartitionCount 4 9 (16 * n + 13) ≡ 0 [MOD 4]
public def regularPartitionCount (l k n : ℕ) : ℕ :=
((Finset.univ : Finset n.Partition).filter fun p => ∀ i ∈ p.parts, ¬ l ∣ i ∧ ¬ k ∣ i).card
WantedExt/Combinatorics/Enumerative/Partition/RegularPartitionsLKWanted.lean:41
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Theorem 14 (jis-2025-25.6.1-thm-14).
Uses 1
Theorem\(b_{4,9}(32n + 25)\) is divisible by \(4\)#●ready to prove
Let \(b_{4,9}(n)\) be the number of partitions of \(n\) with no part divisible by \(4\) or by \(9\). For every natural number \(n\), \(b_{4,9}(32n + 25) \equiv 0 \pmod 4\).
public theorem_wanted regularPartitionCount_four_nine_thirtyTwo_mul_add_twentyFive (n : ℕ) :
regularPartitionCount 4 9 (32 * n + 25) ≡ 0 [MOD 4]
public def regularPartitionCount (l k n : ℕ) : ℕ :=
((Finset.univ : Finset n.Partition).filter fun p => ∀ i ∈ p.parts, ¬ l ∣ i ∧ ¬ k ∣ i).card
WantedExt/Combinatorics/Enumerative/Partition/RegularPartitionsLKWanted.lean:41
Sources
- Manjil P. Saikia and James A. Sellers, Generalizing Recent Results of Kathiravan, Majumdar, Sangale, and Srinivas on
(ℓ, k)-regular Partitions, Journal of Integer Sequences 28 (2025), Article 25.6.1, Theorem 15 (jis-2025-25.6.1-thm-15).
Uses 1
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