A061640 a(n) = !n*n!.

0, 1, 4, 24, 240, 4080, 110880, 4404960, 238452480, 16777393920, 1484592883200, 161180605555200, 21054378333542400, 3256459844769331200, 588451470437627596800, 122827588904844375552000

Offset: 0

Author

Jason Earls, Jun 13 2001

Keywords

• easy
• nonn

Links

• Harry J. Smith, Table of n, a(n) for n = 0..100

Crossrefs

Cf. A000142, A003422.

Programs

Maple

a:=n->sum((n+1)!*j!,j=0..n): seq(a(n), n=-1..15); # Zerinvary Lajos, Jan 08 2007

Mathematica

Table[n!*Sum[i!, {i, 0, n - 1}], {n, 0, 16}] (* Olivier Gérard, Sep 28 2012 *)

PARI

{ for (n=0, 100, L=sum(k=0, n-1, k!); write("b061640.txt", n " ", L*n!) ) } \\ Harry J. Smith, Jul 25 2009

Formula

a(n) = A000142(n)*A003422(n).

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), Jun 19 2001