A132960 - OEIS

%I #10 Sep 29 2017 02:49:38

%S 1,0,3,2,25,94,721,3674,42561,291248,3628801,34254604,479001601,

%T 5337581534,88966701825,1140807642974,20922789888001,321094542593824,

%U 6402373705728001,109338195253235948,2457732174030848001

%N a(n) = n!*Sum_{d|n} (-1)^(d+1)/(d!*(n/d)^d).

%H G. C. Greubel, <a href="/A132960/b132960.txt">Table of n, a(n) for n = 1..450</a>

%F E.g.f.: Sum_{k>0}(1-exp(-x^k/k)).

%t Rest[ Range[0, 22]! CoefficientList[ Series[ - Sum[ Exp[ -x^k/k], {k, 25}], {x, 0, 22}], x]] (* _Robert G. Wilson v_, Sep 13 2007 *)

%o (PARI) a(n) = n!*sumdiv(n, d, (-1)^(d+1)/(d!*(n/d)^d)); \\ _Michel Marcus_, Sep 29 2017

%Y Cf. A005225, A132958, A132959, A132961, A132962, A132963.

%K easy,nonn

%O 1,3

%A _Vladeta Jovovic_, Sep 06 2007

%E More terms from _Robert G. Wilson v_, Sep 13 2007