This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A279223 #9 Feb 16 2025 08:33:37
%S A279223 1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,3,3,3,3,3,3,3,3,4,4,5,5,5,5,5,5,6,6,
%T A279223 7,7,7,7,7,7,8,8,9,9,9,9,9,9,10,10,11,11,12,12,12,12,13,13,14,14,16,
%U A279223 16,16,16,17,17,18,18,20,20,20,20,21,21,22,22,24,24,25,25,26,26,27,27,29,29,31,31,32,32,33,33,35,35,37,37
%N A279223 Expansion of Product_{k>=1} 1/(1 - x^(k*(k+1)*(5*k-2)/6)).
%C A279223 Number of partitions of n into nonzero heptagonal pyramidal numbers (A002413).
%H A279223 M. Bernstein and N. J. A. Sloane, <a href="http://arXiv.org/abs/math.CO/0205301">Some canonical sequences of integers</a>, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210. [Link to arXiv version]
%H A279223 M. Bernstein and N. J. A. Sloane, <a href="/A003633/a003633_1.pdf">Some canonical sequences of integers</a>, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210. [Link to Lin. Alg. Applic. version together with omitted figures]
%H A279223 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HeptagonalPyramidalNumber.html">Heptagonal Pyramidal Number</a>
%H A279223 <a href="/index/Ps#pyramidal_numbers">Index to sequences related to pyramidal numbers</a>
%H A279223 <a href="/index/Par#partN">Index entries for related partition-counting sequences</a>
%F A279223 G.f.: Product_{k>=1} 1/(1 - x^(k*(k+1)*(5*k-2)/6)).
%e A279223 a(9) = 2 because we have [8, 1] and [1, 1, 1, 1, 1, 1, 1, 1, 1].
%t A279223 nmax=95; CoefficientList[Series[Product[1/(1 - x^(k (k + 1) (5 k - 2)/6)), {k, 1, nmax}], {x, 0, nmax}], x]
%Y A279223 Cf. A002413, A068980, A279220, A279221, A279222, A279224.
%K A279223 nonn
%O A279223 0,9
%A A279223 _Ilya Gutkovskiy_, Dec 08 2016