A015020 - OEIS

A015020

q-factorial numbers for q=-7.

1, -6, -258, 77400, 162617400, -2391451484400, -246183190158589200, 177399606828279377520000, 894839274162813664365761520000, -31596243236160097777438406008857120000

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OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..40

Index entries for sequences related to factorial numbers

FORMULA

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

a(1) = 1, a(n) = ((-7)^n - 1)*a(n-1)/(-8). - Vincenzo Librandi, Oct 26 2012

MATHEMATICA

RecurrenceTable[{a[1]==1, a[n]==(((-7)^n - 1) * a[n-1])/(-8)}, a, {n, 15}] (* Vincenzo Librandi, Oct 26 2012 *)

PROG

(Magma) [n le 1 select 1 else ((-7)^n - 1)*Self(n-1)/(-8): n in [1..13]]; // Vincenzo Librandi, Oct 26 2012

CROSSREFS

Sequence in context: A362713 A324091 A221895 * A225166 A003384 A316393

Adjacent sequences: A015017 A015018 A015019 * A015021 A015022 A015023

KEYWORD

sign,easy

AUTHOR

Olivier Gérard

STATUS

approved