login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

a(n) = Sum_{p|n, p prime} (-1)^(n/p+1) * (n-1)!/(p-1)!.
3

%I #13 Oct 04 2023 03:55:20

%S 0,1,1,-6,1,60,1,-5040,20160,347760,1,-59875200,1,6218372160,

%T 47221574400,-1307674368000,1,177843714048000,1,-126713646259200000,

%U 1219830034655232000,51090928092415411200,1,-38778025108327464960000,25852016738884976640000

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

%F E.g.f.: Sum_{p prime} log(1+x^p)/p!.

%t a[n_] := Sum[(-1)^(n/p + 1)*(n - 1)!/(p - 1)!, {p, FactorInteger[n][[;; , 1]]}]; a[1] = 0; Array[a, 25] (* _Amiram Eldar_, Oct 04 2023 *)

%o (PARI) a(n) = sumdiv(n, d, isprime(d)*(-1)^(n/d+1)*(n-1)!/(d-1)!);

%o (PARI) my(N=40, x='x+O('x^N)); concat(0, Vec(serlaplace(sum(k=1, N, isprime(k)*log(1+x^k)/k!))))

%Y Cf. A352005, A352012, A352013.

%K sign

%O 1,4

%A _Seiichi Manyama_, Feb 28 2022