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 A028680 #14 Jul 14 2025 00:25:10
%S A028680 1,306,32023512,1089004102288704,12000667955029147591142400,
%T A028680 42847968954950283704312619696092774400,
%U A028680 49567873660106321460531697392097352394556112948428800,18578701620081137383821309406407591330835087924034550043168000809369600
%N A028680 Pseudo Galois numbers for d=18.
%H A028680 Vincenzo Librandi, <a href="/A028680/b028680.txt">Table of n, a(n) for n = 0..28</a>
%F A028680 a(n) = 18^n * Product_{k=0..n-1} (18^n - 18^k).
%F A028680 a(n) ~ c * 18^(n^2+n), where c = Product_{k>=1} (1 - 1/18^k) = 0.941358555546... . - _Amiram Eldar_, Jul 14 2025
%t A028680 FoldList[ #1*18^#2 (18^#2-1)&, 1, Range[ 20 ] ]
%t A028680 a[n_] := 18^n * Product[18^n - 18^k, {k, 0, n-1}]; Array[a, 8, 0] (* _Amiram Eldar_, Jul 14 2025 *)
%o A028680 (PARI) a(n) = 18^n * prod(k = 0, n-1, 18^n - 18^k); \\ _Amiram Eldar_, Jul 14 2025
%Y A028680 Cf. A028668, A028670, A028671, A028672, A028674, A028676, A028677, A028678, A028682, A028683, A028684, A028686.
%K A028680 nonn
%O A028680 0,2
%A A028680 _Olivier Gérard_