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%I #17 Mar 10 2018 07:34:16
%S 1,8,70,728,9027,132136,2254620,44262200,987183525,24718587592,
%T 687457908306,21034757596184,702270963692039,25400848001674856,
%U 989240042333246072,41263578858484555512,1835070614332428285513
%N Self-convolution of 1,4,27,256,3125,46656,... (cf. A000312).
%F a(n) = Sum{k=1..n} k^k * (n+1-k)^(n+1-k).
%F a(n) ~ 2 * n^n. - _Vaclav Kotesovec_, Mar 10 2018
%e a(4) = 1^1 *4^4 +2^2 *3^3 +3^3 *2^2 +4^4 *1^1 = 1*256 +4*27 +27*4 +256*1 = 728.
%t nn=20;f[x_]=Sum[n^n x^n,{n,1,nn}];CoefficientList[Series[f[x]^2/x^2,{x,0,nn}],x] (* _Geoffrey Critzer_, Nov 05 2013 *)
%t Table[Sum[k^k*(n+1-k)^(n+1-k), {k, 1, n}], {n, 1, 20}] (* _Vaclav Kotesovec_, Mar 10 2018 *)
%K nonn,easy
%O 1,2
%A _Leroy Quet_, Feb 11 2000
%E More terms from _James A. Sellers_, Feb 22 2000
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