A034716 - OEIS

%I #12 Nov 13 2022 07:13:46

%S 1,4,12,52,240,1464,10080,80736,725796,7258080,79833600,958006368,

%T 12454041600,174356602560,2615348737440,41845579937856,

%U 711374856192000,12804747412916160,243290200817664000,4865804016367800960,102181884343418940480,2248001455555375027200

%N Dirichlet convolution of factorials with themselves.

%H Seiichi Manyama, <a href="/A034716/b034716.txt">Table of n, a(n) for n = 1..449</a>

%F a(n) ~ 2 * n!. - _Vaclav Kotesovec_, Jan 28 2019

%t Table[Sum[d!*(n/d)!, {d, Divisors[n]}], {n, 1, 25}] (* _Vaclav Kotesovec_, Jan 28 2019 *)

%o (PARI) a(n)=sumdiv(n,d, (d!) * (n/d)! );  /* _Joerg Arndt_, Oct 07 2012 */

%K nonn

%O 1,2

%A _Erich Friedman_