%I #9 Apr 12 2021 12:14:48
%S 1,1,10,91,865,8155,77251,730435,6905560,65233120,615847378,
%T 5810270782,54784324495,516250199827,4862041512625,45765734635702,
%U 430560567351208,4048630897384450,38051334554031551,357459295903931045,3356488167698692226,31503001136703776561
%N Expansion of Product_{k>=1} 1 / (1 - x^k)^(9^(k-1)).
%F a(n) ~ exp(2*sqrt(n/9) - 1/18 + c/9) * 9^(n - 1/4) / (2*sqrt(Pi)*n^(3/4)), where c = Sum_{j>=2} 1/(j * (9^(j-1) - 1)). - _Vaclav Kotesovec_, Apr 12 2021
%p a:= proc(n) option remember; `if`(n=0, 1, add(a(n-j)*add(
%p d*9^(d-1), d=numtheory[divisors](j)), j=1..n)/n)
%p end:
%p seq(a(n), n=0..21); # _Alois P. Heinz_, Apr 12 2021
%t nmax = 21; CoefficientList[Series[Product[1/(1 - x^k)^(9^(k - 1)), {k, 1, nmax}], {x, 0, nmax}], x]
%t a[n_] := a[n] = If[n == 0, 1, (1/n) Sum[Sum[d 9^(d - 1), {d, Divisors[k]}] a[n - k], {k, 1, n}]]; Table[a[n], {n, 0, 21}]
%Y Cf. A034691, A104460, A144073, A343349, A343350, A343351, A343352, A343353, A343355.
%K nonn
%O 0,3
%A _Ilya Gutkovskiy_, Apr 12 2021
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