A173322 a(n) = 4*n! + 1.

5, 5, 9, 25, 97, 481, 2881, 20161, 161281, 1451521, 14515201, 159667201, 1916006401, 24908083201, 348713164801, 5230697472001, 83691159552001, 1422749712384001, 25609494822912001, 486580401635328001, 9731608032706560001, 204363768686837760001

Offset: 0

Author

Vincenzo Librandi, Feb 16 2010

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..200

Crossrefs

Cf. sequences of the type k*n!+1: A038507 (k=1), A052898 (k=2), A173324 (k=3), this sequence, A173319 (k=5), A173314 (k=6).

Programs

Magma

[4*Factorial(n) + 1: n in [0..25]]; // Vincenzo Librandi, Sep 29 2013

Magma

[5] cat [n eq 1 select n+4 else n*Self(n-1)-n+1: n in [1..25] ]; // Vincenzo Librandi, Sep 29 2013

Maple

a:= proc(n) if n=0 then 5 else a(n) := n*a(n-1)-n+1 fi end: seq (a(n), n=0..25);  # Sergei N. Gladkovskii, Jul 04 2012

Mathematica

4*Range[0,20]!+1 (* Harvey P. Dale, Jun 26 2012 *)
Table[4 n! + 1, {n, 0, 21}] (* Vincenzo Librandi, Sep 29 2013 *)

Formula

a(0) = 5, a(n) = n*a(n-1)-n+1. - Sergei N. Gladkovskii, Jul 04 2012