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A343352 Expansion of Product_{k>=1} 1 / (1 - x^k)^(7^(k-1)). 7

%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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Last modified March 28 18:04 EDT 2024. Contains 371254 sequences. (Running on oeis4.)