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 A266647 #8 Jan 05 2016 11:19:43
%S A266647 1,2,4,9,15,27,46,75,118,187,285,429,639,935,1354,1945,2758,3878,5417,
%T A266647 7493,10300,14070,19087,25741,34542,46081,61185,80869,106391,139368,
%U A266647 181867,236357,306060,394939,507860,650946,831792,1059600,1345920,1704880,2153682
%N A266647 Expansion of Product_{k>=1} (1 + x^k + x^(3*k)) / (1 - x^k).
%C A266647 Convolution of A264905 and A000041.
%H A266647 Vaclav Kotesovec, <a href="/A266647/b266647.txt">Table of n, a(n) for n = 0..5000</a>
%F A266647 a(n) ~ sqrt(6*c + Pi^2) * exp(sqrt((4*c + 2*Pi^2/3)*n)) / (12*Pi*n), where c = Integral_{0..infinity} log(1 + exp(-x) + exp(-3*x)) dx = 0.9953865985263189816963357718655148864441174218433250148867... . - _Vaclav Kotesovec_, Jan 05 2016
%t A266647 nmax = 50; CoefficientList[Series[Product[(1+x^k+x^(3*k))/(1-x^k), {k, 1, nmax}], {x, 0, nmax}], x]
%Y A266647 Cf. A100405, A264905, A266648, A266649, A266650.
%K A266647 nonn
%O A266647 0,2
%A A266647 _Vaclav Kotesovec_, Jan 02 2016