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%I #13 Jul 17 2023 00:59:17
%S 4,26,128,1219,12556,195278,3294292,67773349,1550075836,40097713880,
%T 1141246682808,35686524105658,1211500426369572,44454809534927314,
%U 1751576172678539608,73789791194939982793,3308961047545347057848,157387135278770854655312
%N Expansion of Sum_{k>0} (1/(1 - (k*x)^k)^4 - 1).
%F a(n) = Sum_{d|n} (n/d)^n * binomial(d+3,3).
%t a[n_] := DivisorSum[n, (n/#)^n * Binomial[# + 3, 3] &]; Array[a, 20] (* _Amiram Eldar_, Jul 17 2023 *)
%o (PARI) a(n) = sumdiv(n, d, (n/d)^n*binomial(d+3, 3));
%Y Cf. A023887, A338663, A363646, A363647.
%Y Cf. A363640.
%K nonn
%O 1,1
%A _Seiichi Manyama_, Jun 13 2023
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