A015018 q-factorial numbers for q=-5.

1, -4, -84, 8736, 4551456, -11851991424, -154324780331904, 10047160498728278016, 3270561732706527788046336, -5323179358400075453935368658944, -43320145405426340445710562789228109824, 1762701221841919957075369153792221868461981696

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) = ((-5)^n - 1)*a(n-1)/(-6). - Vincenzo Librandi, Oct 26 2012

Mathematica

RecurrenceTable[{a[1]==1, a[n]==(((-5)^n - 1) * a[n-1])/(-6)}, a, {n, 15}] (* Vincenzo Librandi, Oct 26 2012 *)

Prog

(Magma) [n le 1 select 1 else ((-5)^n - 1)*Self(n-1)/(-6): n in [1..18]]; // Vincenzo Librandi, Oct 26 2012

Crossrefs

Sequence in context: A173211 A109901 A367522 * A204245 A287248 A225164

Adjacent sequences: A015015 A015016 A015017 * A015019 A015020 A015021

Keyword

sign,easy

Author

Olivier Gérard

Status

approved