A281596 a(n) = ((n-2)^n - 2*(n-1)^n + n^n)/2.

0, 0, 1, 6, 55, 660, 9751, 170898, 3463615, 79669320, 2050086511, 58346365110, 1819621847407, 61705703989020, 2260586259354151, 88971796139662842, 3743940350046570751, 167735288431662235920, 7971302827015366403551, 400510700317394780627934, 21212944650652080893863087

Offset: 0

Author

Peter Luschny, Jan 26 2017

Keywords

• nonn

Links

• Paolo Xausa, Table of n, a(n) for n = 0..380

Crossrefs

Cf. A000312, A045531, A281595.

Programs

Maple

a := n -> ((n-2)^n-2*(n-1)^n+n^n)/2:
seq(a(n), n=0..21);

Mathematica

A281596[n_] := If[n == 0, 0, ((n-2)^n - 2*(n-1)^n + n^n)/2];
Array[A281596, 25, 0] (* Paolo Xausa, Jul 10 2024 *)

Formula

a(n) ~ n^n*(1/2+(1/2-1/n)*e^(-2)+(1/(2*n)-1)*e^(-1)).