A015017 q-factorial numbers for q=-4.

1, -3, -39, 1989, 407745, -333943155, -1094331718935, 14343405840081045, 752010424789609108305, -157707866234752874148183075, -132294978377551030760819002477575, 443908259132104963309174796130361690725

Offset

1,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..50

Index entries for sequences related to factorial numbers

Formula

Prod_{k=1}^{n} (q^k - 1) / (q - 1).

a(1) = 1, a(n) = ((-4)^n - 1)*a(n-1)/(-5). - Vincenzo Librandi, Oct 26 2012

Mathematica

RecurrenceTable[{a[1]==1, a[n]==(((-4)^n-1) * a[n-1])/(-5)}, a, {n, 18}] (* Vincenzo Librandi, Oct 26 2012 *)

Prog

(Magma) [n le 1 select 1 else ((-4)^n - 1)*Self(n-1)/(-5): n in [1..18]]; // Vincenzo Librandi, Oct 26 2012

Crossrefs

Sequence in context: A369945 A084881 A193122 * A210921 A290516 A210925

Adjacent sequences: A015014 A015015 A015016 * A015018 A015019 A015020

Keyword

sign,easy

Author

Olivier Gérard

Status

approved