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 A340647 #7 Jan 14 2021 11:14:57 %S A340647 1,1,0,2,1,3,2,4,5,6,8,8,14,12,20,18,31,27,42,40,60,60,80,86,111,124, %T A340647 146,174,199,241,262,328,353,444,464,590,620,780,812,1020,1075,1326, %U A340647 1400,1710,1833,2198,2370,2804,3072,3570,3936,4522,5048,5713,6414,7190 %N A340647 G.f.: Sum_{k>=0} x^(k^2) / Product_{j=1..k} (1 - x^(2*j))^2. %H A340647 Vaclav Kotesovec, <a href="/A340647/b340647.txt">Table of n, a(n) for n = 0..10000</a> %H A340647 Vaclav Kotesovec, <a href="/A340647/a340647.jpg">Graph - the asymptotic ratio</a> %F A340647 a(n) = A006950(n) - A340623(n). %F A340647 a(n) ~ exp(Pi*sqrt(n/2)) / (4*sqrt(2)*n). %t A340647 nmax = 100; CoefficientList[Series[Sum[x^(k^2)/Product[(1-x^(2*j))^2, {j, 1, k}], {k, 0, Sqrt[nmax]}], {x, 0, nmax}], x] %Y A340647 Cf. A000700, A006950, A340623. %K A340647 nonn %O A340647 0,4 %A A340647 _Vaclav Kotesovec_, Jan 14 2021