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 A338678 #11 May 09 2021 02:31:15 %S A338678 1,1,10,91,901,8191,81091,737191,7239142,66288142,646149322, %T A338678 5912729632,57664985653,527352541453,5111015223223,46998961540624, %U A338678 453182267869615,4163124744738505,40151590267580785,368699990679135946,3540322181970716707,32632895079429817528,312061810101214595698 %N A338678 Expansion of Product_{k>=1} 1 / (1 - 9^(k-1)*x^k). %F A338678 a(n) = Sum_{k=0..n} p(n,k) * 9^(n-k), where p(n,k) = number of partitions of n into k parts. %F A338678 a(n) ~ sqrt(2) * polylog(2, 1/9)^(1/4) * 9^(n - 1/2) * exp(2*sqrt(polylog(2, 1/9)*n)) / (sqrt(Pi)*n^(3/4)). - _Vaclav Kotesovec_, May 09 2021 %t A338678 nmax = 22; CoefficientList[Series[Product[1/(1 - 9^(k - 1) x^k), {k, 1, nmax}], {x, 0, nmax}], x] %t A338678 Table[Sum[Length[IntegerPartitions[n, {k}]] 9^(n - k), {k, 0, n}], {n, 0, 22}] %t A338678 a[n_] := a[n] = If[n == 0, 1, (1/n) Sum[Sum[d 9^(k - k/d), {d, Divisors[k]}] a[n - k], {k, 1, n}]]; Table[a[n], {n, 0, 22}] %Y A338678 Cf. A008284, A075900, A246941, A300579, A338673, A338674, A338675, A338676, A338677, A338679. %K A338678 nonn %O A338678 0,3 %A A338678 _Ilya Gutkovskiy_, Apr 23 2021