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%I #45 Aug 30 2023 02:00:21
%S 1,5,217,331793,24883200001,139314069504046721,
%T 82606411253903523840000001,6984964247141514123629140487675314433,
%U 109110688415571316480344899355894085582848010077697,395940866122425193243875570782668457763038823019173642240000001025
%N a(n) = Sum_{d|n} (d!)^n.
%H Seiichi Manyama, <a href="/A346196/b346196.txt">Table of n, a(n) for n = 1..30</a>
%F G.f.: Sum_{k >= 1} (k! * x)^k/(1 - (k! * x)^k).
%F If p is prime, a(p) = 1 + (p!)^p.
%t a[n_] := DivisorSum[n, (#!)^n &]; Array[a, 10] (* _Amiram Eldar_, Aug 30 2023 *)
%o (PARI) a(n) = sumdiv(n, d, d!^n);
%o (PARI) my(N=20, x='x+O('x^N)); Vec(sum(k=1, N, (k!*x)^k/(1-(k!*x)^k)))
%Y Cf. A023887, A036739, A217576, A345465, A348146.
%K nonn
%O 1,2
%A _Seiichi Manyama_, Jul 10 2021