This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A015028 #32 Aug 10 2025 02:38:14
%S A015028 1,1,-12,-1884,3843360,101929750560,-35142523960072320,
%T A015028 -157510092662430660915840,9177558663913662855639573043200,
%U A015028 6951672507594336724476921764731548211200,-68453363408439970530162052940526993784438155878400,-8762814767092584880014595182992133840006733019391100715212800
%N A015028 q-factorial numbers for q=-13.
%H A015028 Vincenzo Librandi, <a href="/A015028/b015028.txt">Table of n, a(n) for n = 0..40</a>
%H A015028 <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>.
%F A015028 a(n) = Product_{k=1..n} ((-13)^k - 1) / (-13 - 1).
%F A015028 a(0) = 1, a(n) = ((-13)^n - 1)*a(n-1)/(-14). - _Vincenzo Librandi_, Oct 26 2012
%F A015028 a(n) ~ (-1)^floor(n/2) * c * 13^(n*(n+1)/2) / 14^n, where c = Product_{k>=1} (1 - 1/(-13)^k) = 1.07100320793234536419... . - _Amiram Eldar_, Aug 10 2025
%t A015028 RecurrenceTable[{a[1]==1, a[n]==(((-13)^n - 1) a[n-1])/(-14)}, a, {n, 15}] (* _Vincenzo Librandi_, Oct 26 2012 *)
%o A015028 (Magma) [1] cat [n le 1 select 1 else ((-13)^n - 1)*Self(n-1)/(-14): n in [1..13]]; // _Vincenzo Librandi_, Oct 26 2012
%Y A015028 Column k=13 of A384454.
%K A015028 sign,easy
%O A015028 0,3
%A A015028 _Olivier Gérard_
%E A015028 a(0)=1 prepended by _Seiichi Manyama_, May 31 2025