%I #17 Sep 08 2022 08:44:39

%S 1,-2,-14,280,17080,-3108560,-1700382320,2788627004800,

%T 13722833490620800,-202576467988544249600,-8971504037808659182035200,

%U 1191954026463258458925196672000,475090227821752019816863814722432000

%N q-factorial numbers for q=-3.

%H Vincenzo Librandi, <a href="/A015015/b015015.txt">Table of n, a(n) for n = 1..60</a>

%H <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>

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

%F a(1) = 1, a(n) = ((-3)^n - 1)*a(n-1)/(-4). - _Vincenzo Librandi_, Oct 26 2012

%t RecurrenceTable[{a[1]==1, a[n]==(((-3)^n - 1) * a[n-1])/(-4)}, a, {n, 18}] (* _Vincenzo Librandi_, Oct 26 2012 *)

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

%K sign,easy

%O 1,2

%A _Olivier Gérard_