A161474 Triple factorials n!!!: a(n) = n*a(n-3).

1, 1, 1, 3, 4, 5, 18, 28, 40, 162, 280, 440, 1944, 3640, 6160, 29160, 58240, 104720, 524880, 1106560, 2094400, 11022480, 24344320, 48171200, 264539520, 608608000, 1252451200, 7142567040, 17041024000, 36321084800, 214277011200, 528271744000, 1162274713600

Offset: 0

Author

Asbel Torres da Cunha (asbeltc(AT)gmail.com), Jun 11 2009

Keywords

• nonn

Comments

This definition of triple factorials starts with a(1)=a(2)=1. The main version is A007661.

Links

• Wikipedia, Multifactorials

Crossrefs

Cf. A002110, A006882, A001813.

Programs

Magma

TripleFactorial:=func; [TripleFactorial(n): n in [1..35]]; // Vincenzo Librandi, Apr 08 2016

Maple

A161474 := proc(n) if n < 3 then 1 ; else procname(n-3)*n ; fi; end: seq(A161474(n),n=0..80) ; # R. J. Mathar, Jun 16 2009

Mathematica

multiFactorialRev[n_, k_] := If[n < k, 1, If[n >= k, n*multiFactorialRev[n - k, k]]]; Array[ multiFactorialRev[#, 3] &, 32] (* Robert G. Wilson v, Aug 29 2012 *)

Extensions

Corrected and extended by R. J. Mathar, Jun 16 2009

a(0)=1 prepended by Alois P. Heinz, May 06 2020