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 A386880 #8 Aug 06 2025 11:53:28
%S A386880 1,1,6,56,715,11628,230230,5379616,145008513,4431613550,151473214816,
%T A386880 5727160371180,237377895350076,10704005376506540,521748877569771510,
%U A386880 27338999059076777600,1532576541123942256285,91527291781199227579626,5801648509628587739612170,389032765009190361630625600
%N A386880 a(n) = [x^n] 1/(1 - x)^(n*(n+1)/2).
%F A386880 a(n) ~ exp(n+2) * n^(n - 1/2) / (sqrt(Pi) * 2^(n + 1/2)).
%F A386880 For n > 0, a(n) = binomial(n*(n+3)/2, n) * (n+1)/(n+3).
%t A386880 Table[SeriesCoefficient[1/(1-x)^(n*(n+1)/2), {x, 0, n}], {n, 0, 25}]
%t A386880 Join[{1}, Table[Binomial[n*(n + 3)/2, n]*(n + 1)/(n + 3), {n, 1, 25}]]
%Y A386880 Cf. A014068, A054688, A116508, A177234, A386879.
%K A386880 nonn
%O A386880 0,3
%A A386880 _Vaclav Kotesovec_, Aug 06 2025