cp's OEIS Frontend

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.

A280541 G.f.: Product_{i>=1, j>=1} (1 + x^(i*j))^(i*j).

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%I A280541 #25 Sep 30 2024 20:35:11
%S A280541 1,1,4,10,24,52,125,253,549,1126,2290,4525,8987,17259,33174,62669,
%T A280541 117425,217295,399904,726984,1314257,2354807,4191671,7405590,13009916,
%U A280541 22696115,39384232,67937488,116584833,199001304,338076500,571507377,961855945,1611567819
%N A280541 G.f.: Product_{i>=1, j>=1} (1 + x^(i*j))^(i*j).
%H A280541 Vaclav Kotesovec, <a href="/A280541/b280541.txt">Table of n, a(n) for n = 0..10000</a>
%H A280541 Lida Ahmadi, Ricardo Gómez Aíza, and Mark Daniel Ward, <a href="https://doi.org/10.1007/s44007-024-00134-w">A unified treatment of families of partition functions</a>, La Matematica (2024). Preprint available as <a href="https://arxiv.org/abs/2303.02240">arXiv:2303.02240</a> [math.CO], 2023.
%F A280541 G.f.: Product_{k>=1} (1 + x^k)^(k*d(k)), where d(k) = number of divisors of k (A000005). - _Ilya Gutkovskiy_, Aug 26 2018
%F A280541 Conjecture: log(a(n)) ~ 3 * Zeta(3)^(1/3) * log(n)^(1/3) * n^(2/3) / 2^(4/3). - _Vaclav Kotesovec_, Aug 29 2018
%t A280541 nmax = 50; CoefficientList[Series[Product[(1+x^(i*j))^(i*j), {i, 1, nmax}, {j, 1, nmax}], {x, 0, nmax}], x]
%t A280541 nmax = 50; s = 1 + x; Do[s *= Sum[Binomial[k*DivisorSigma[0, k], j]*x^(j*k), {j, 0, nmax/k}]; s = Expand[s]; s = Take[s, Min[nmax + 1, Exponent[s, x] + 1, Length[s]]];, {k, 2, nmax}]; CoefficientList[s, x] (* _Vaclav Kotesovec_, Aug 27 2018 *)
%Y A280541 Cf. A000005, A006171, A038040, A061256, A107742, A192065, A280540.
%K A280541 nonn
%O A280541 0,3
%A A280541 _Vaclav Kotesovec_, Jan 05 2017