English

Combinatorial proofs of some identities on overpartitions with repeated smallest non-overlined part

Combinatorics 2026-02-03 v2

Abstract

Let sptk(n)\overline{\mathrm{spt}}k(n) denote the number of overpartitions of nn where the smallest non-overlined part, say s(π)s(\pi), appears kk times and every overlined part is bigger than s(π)s(\pi). Let sptko(n)\overline{\mathrm{spt}}k_o(n) denote the number of overpartitions of nn where the smallest non-overlined part appears kk times, every overlined part is bigger than s(π)s(\pi) and all parts other than s(π)s(\pi) are incongruent modulo 22 with s(π)s(\pi). Also, let be(k,n)b_e(k,n) (resp., bo(k,n)b_o(k,n)) denote the number of overpartitions of nn counted by sptko(n)\overline{\mathrm{spt}}k_o(n) where the number of parts greater than s(π)s(\pi) is even (resp., odd), and let sptko(n)=be(k,n)bo(k,n).\overline{\mathrm{spt}}k_o'(n)=b_e(k,n)-b_o(k,n). Recently, Malik and Sarma (arXiv:2601.15601v1) expressed the generating functions of these partition functions in terms of linear combinations of qq-series with polynomials in qq as coefficients. As corollaries, they derived some partition identities involving the functions for k=1k=1 and sought for combinatorial proofs of their results. In this paper, we present some desired proofs.

Keywords

Cite

@article{arxiv.2601.19736,
  title  = {Combinatorial proofs of some identities on overpartitions with repeated smallest non-overlined part},
  author = {Nayandeep Deka Baruah and Haijun Li and Pankaj Jyoti Mahanta},
  journal= {arXiv preprint arXiv:2601.19736},
  year   = {2026}
}