A015015 q-factorial numbers for q=-3.

1, -2, -14, 280, 17080, -3108560, -1700382320, 2788627004800, 13722833490620800, -202576467988544249600, -8971504037808659182035200, 1191954026463258458925196672000, 475090227821752019816863814722432000

Offset

1,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..60

Index entries for sequences related to factorial numbers

Formula

a(n) = product_{k=1..n} ((-3)^k - 1)/(-3 - 1).

a(1) = 1, a(n) = ((-3)^n - 1)*a(n-1)/(-4). - Vincenzo Librandi, Oct 26 2012

Mathematica

RecurrenceTable[{a[1]==1, a[n]==(((-3)^n - 1) * a[n-1])/(-4)}, a, {n, 18}] (* Vincenzo Librandi, Oct 26 2012 *)

Prog

(Magma) [n le 1 select 1 else ((-3)^n - 1)*Self(n-1)/(-4): n in [1..18]]; // Vincenzo Librandi, Oct 26 2012

Crossrefs

Sequence in context: A018803 A217474 A132695 * A355132 A355133 A128087

Adjacent sequences: A015012 A015013 A015014 * A015016 A015017 A015018

Keyword

sign,easy

Author

Olivier Gérard

Status

approved