%I #19 Feb 20 2023 12:25:42
%S 1,4,27,257,3125,46665,823543,16777312,387420490,10000001250,
%T 285311670611,8916100467712,302875106592253,11112006825910963,
%U 437893890380859625,18446744073716891649,827240261886336764177,39346408075296709766628,1978419655660313589123979
%N a(n) = Sum_{d|n} d^(d - n/d) * binomial(d, n/d).
%H Winston de Greef, <a href="/A338693/b338693.txt">Table of n, a(n) for n = 1..385</a>
%F G.f.: Sum_{k>=1} ( (k + x^k)^k - k^k ).
%F If p is prime, a(p) = p^p.
%t a[n_] := DivisorSum[n, #^(# - n/#) * Binomial[#, n/#] &]; Array[a, 20] (* _Amiram Eldar_, Apr 24 2021 *)
%o (PARI) a(n) = sumdiv(n, d, d^(d-n/d)* binomial(d, n/d));
%o (PARI) N=20; x='x+O('x^N); Vec(sum(k=1, N, (k+x^k)^k-k^k))
%Y Cf. A318636, A318637, A318638, A338685, A338694.
%K nonn
%O 1,2
%A _Seiichi Manyama_, Apr 24 2021