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 A028694 #17 Jul 15 2025 11:02:16
%S A028694 1,24,14976,233985024,91400166014976,892579654839833985024,
%T A028694 217914953902301689160166014976,
%U A028694 1330047325845938129350664710839833985024,202949115880923695556030391039325175289160166014976,774189437411767935420978172981557217629743778824710839833985024
%N A028694 25-factorial numbers.
%H A028694 Vincenzo Librandi, <a href="/A028694/b028694.txt">Table of n, a(n) for n = 0..37</a>
%H A028694 <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>.
%F A028694 From _Amiram Eldar_, Jul 14 2025: (Start)
%F A028694 a(n) = Product_{k=1..n} (25^k-1).
%F A028694 a(n) ~ c * 25^(n*(n+1)/2), where c = Product_{k>=1} (1 - 1/25^k) = 0.958400102563... . (End)
%t A028694 FoldList[ #1 (25^#2-1)&, 1, Range[ 20 ] ]
%t A028694 a[n_] := Abs[QPochhammer[25, 25, n]]; Array[a, 10, 0] (* _Amiram Eldar_, Jul 14 2025 *)
%o A028694 (PARI) a(n) = prod(k = 1, n, 25^k - 1); \\ _Amiram Eldar_, Jul 14 2025
%Y A028694 Cf. A005329, A027871, A027637, A027872, A027873, A027875, A027876, A027877, A027878, A027879, A027880, A028692, A028693.
%K A028694 nonn
%O A028694 0,2
%A A028694 _Olivier Gérard_