%I #9 Apr 12 2021 12:14:01
%S 1,1,8,57,428,3172,23689,176324,1312550,9757798,72480269,537854094,
%T 3987751860,29540543908,218652961074,1617159619805,11951595353413,
%U 88264810625245,651404299886762,4804261815210433,35410065096578748,260832137791524693,1920169120639498017,14127684273966098698
%N Expansion of Product_{k>=1} 1 / (1 - x^k)^(7^(k-1)).
%F a(n) ~ exp(2*sqrt(n/7) - 1/14 + c/7) * 7^(n - 1/4) / (2*sqrt(Pi)*n^(3/4)), where c = Sum_{j>=2} 1/(j * (7^(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*7^(d-1), d=numtheory[divisors](j)), j=1..n)/n)
%p end:
%p seq(a(n), n=0..23); # _Alois P. Heinz_, Apr 12 2021
%t nmax = 23; CoefficientList[Series[Product[1/(1 - x^k)^(7^(k - 1)), {k, 1, nmax}], {x, 0, nmax}], x]
%t a[n_] := a[n] = If[n == 0, 1, (1/n) Sum[Sum[d 7^(d - 1), {d, Divisors[k]}] a[n - k], {k, 1, n}]]; Table[a[n], {n, 0, 23}]
%Y Cf. A034691, A104460, A144071, A343349, A343350, A343351, A343353, A343354, A343355.
%K nonn
%O 0,3
%A _Ilya Gutkovskiy_, Apr 12 2021
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