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Congruences modulo powers of $7$ for partitions with colored odd parts
Abstract
Let ak(n) denote the number of partitions of n in which even parts occur in one color and odd parts may occur in k colors. We prove infinite families of congruences modulo powers of $7$ for ak(n) when k ∈ {4,5,7}. For each positive integer α, let λk,α be the least nonnegative solution of 24λk,α≡−(k−2)pmod7α. Then, we show that ak(7αn+λk,α) ≡ 0pmod7⌊(α+1)/2⌋ for every nonnegative integer n. These results extend congruences modulo $7$ of Hirschhorn and Sellers (2026) and complement Chen's (2025) congruences for the reciprocal crank parity function a3(n).
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BibTeX
@misc{maity2026congruences,
title = {{Congruences modulo powers of $7$ for partitions with colored odd parts}},
author = {Saikat Maity and Manjil P. Saikia and Prabal Talukdar},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.35292},
eprint = {2610.35292},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.35292},
}
RIS
TY - UNPB
TI - Congruences modulo powers of $7$ for partitions with colored odd parts
AU - Saikat Maity
AU - Manjil P. Saikia
AU - Prabal Talukdar
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.35292
UR - https://arxiv.org/abs/2610.35292
AB - Let a_k(n) denote the number of partitions of n in which even parts occur in one color and odd parts may occur in k colors. We prove infinite families of congruences modulo powers of $7$ for a_k(n) when k ∈ {4,5,7}. For each positive integer α, let λ_k,α be the least nonnegative solution of 24λ_k,α≡−(k−2)pmod7^α. Then, we show that a_k(7^αn+λ_k,α) ≡ 0pmod7^⌊(α+1)/2⌋ for every nonnegative integer n. These results extend congruences modulo $7$ of Hirschhorn and Sellers (2026) and complement Chen's (2025) congruences for the reciprocal crank parity function a_3(n).
ER -