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 A015002 #34 Jul 06 2025 10:11:59
%S A015002 1,1,5,105,8925,3043425,4154275125,22686496457625,495586515116818125,
%T A015002 43304845277422684580625,15136126045591163828042953125,
%U A015002 21161832960467051739150680807015625,118345540457280742481284963098558216328125,2647344887069536899904944217513732945696167890625
%N A015002 q-factorial numbers for q=4.
%H A015002 Vincenzo Librandi, <a href="/A015002/b015002.txt">Table of n, a(n) for n = 0..50</a>
%H A015002 <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>.
%F A015002 a(n) = Product_{k=1..n} (q^k - 1) / (q - 1) with q=4.
%F A015002 a(0) = 1, a(n) = (4^n-1)*a(n-1)/3. - _Vincenzo Librandi_, Oct 27 2012
%F A015002 From _Amiram Eldar_, Jul 05 2025: (Start)
%F A015002 a(n) = Product_{k=1..n} A002450(k).
%F A015002 a(n) ~ c * 2^(n*(n+1))/3^n, where c = A100221. (End)
%t A015002 RecurrenceTable[{a[1]==1, a[n]==((4^n - 1) * a[n-1])/3}, a, {n, 15}] (* _Vincenzo Librandi_, Oct 27 2012 *)
%t A015002 Table[QFactorial[n, 4], {n, 15}] (* _Bruno Berselli_, Aug 14 2013 *)
%o A015002 (Magma) [n le 1 select 1 else (4^n-1)*Self(n-1)/3: n in [1..15]]; // _Vincenzo Librandi_, Oct 22 2012
%Y A015002 Cf. A015001, A015004, A015005, A015006, A015007, A015008, A015009, A015011.
%Y A015002 Column q=4 of A069777.
%Y A015002 Cf. A002450, A100221.
%K A015002 nonn,easy
%O A015002 0,3
%A A015002 _Olivier Gérard_
%E A015002 a(0)=1 prepended by _Alois P. Heinz_, Sep 08 2021