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 A028682 #14 Jul 14 2025 00:25:02
%S A028682 1,380,60648000,3880986816000000,99352641531709440000000000,
%T A028682 1017370731356251764129792000000000000000,
%U A028682 4167150450523480419075515127693312000000000000000000000,6827459292803717741943269048796063017352560640000000000000000000000000000
%N A028682 Pseudo Galois numbers for d=20.
%H A028682 Vincenzo Librandi, <a href="/A028682/b028682.txt">Table of n, a(n) for n = 0..27</a>
%F A028682 a(n) = 20^n * Product_{k=0..n-1} (20^n - 20^k).
%F A028682 a(n) ~ c * 20^(n^2+n), where c = Product_{k>=1} (1 - 1/20^k) = 0.947500313281... . - _Amiram Eldar_, Jul 14 2025
%t A028682 FoldList[ #1*20^#2 (20^#2-1)&, 1, Range[ 20 ] ]
%t A028682 a[n_] := 20^n * Product[20^n - 20^k, {k, 0, n-1}]; Array[a, 8, 0] (* _Amiram Eldar_, Jul 14 2025 *)
%o A028682 (PARI) a(n) = 20^n * prod(k = 0, n-1, 20^n - 20^k); \\ _Amiram Eldar_, Jul 14 2025
%Y A028682 Cf. A028668, A028670, A028671, A028672, A028674, A028676, A028677, A028678, A028680, A028683, A028684, A028686.
%K A028682 nonn
%O A028682 0,2
%A A028682 _Olivier Gérard_