%I #3 Dec 05 2013 19:56:00
%S 1,3,24,250,3115,46641,823522,16777188,387420453,9999999955,
%T 285311670556,8916100448190,302875106592175,11112006825557925,
%U 437893890380859270,18446744073709551496,827240261886336764041
%N a(n) = n^n - n(n-1)/2.
%t Table[n^n - n (n - 1)/2, {n, 20}]
%K nonn
%O 1,2
%A _Amarnath Murthy_, Mar 21 2003
%E More terms from _Harvey P. Dale_, Mar 22 2003