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 A028677 #14 Jul 14 2025 00:25:13
%S A028677 1,210,10584000,120522654000000,308880278577360000000000,
%T A028677 178115698742031918598500000000000000,
%U A028677 23109857603759312583902403410250000000000000000000,674644359535320835775869151538023145415195312500000000000000000000
%N A028677 Pseudo Galois numbers for d=15.
%H A028677 Vincenzo Librandi, <a href="/A028677/b028677.txt">Table of n, a(n) for n = 0..29</a>
%F A028677 a(n) = 15^n * Product_{k=0..n-1} (15^n - 15^k).
%F A028677 a(n) ~ c * 15^(n^2+n), where c = Product_{k>=1} (1 - 1/15^k) = 0.928890211614... . - _Amiram Eldar_, Jul 13 2025
%t A028677 FoldList[ #1*15^#2 (15^#2-1)&, 1, Range[ 20 ] ]
%t A028677 a[n_] := 15^n * Product[15^n - 15^k, {k, 0, n-1}]; Array[a, 8, 0] (* _Amiram Eldar_, Jul 13 2025 *)
%o A028677 (PARI) a(n) = 15^n * prod(k = 0, n-1, 15^n - 15^k); \\ _Amiram Eldar_, Jul 13 2025
%Y A028677 Cf. A028668, A028670, A028671, A028672, A028674, A028676, A028678, A028680, A028682, A028683, A028684, A028686.
%K A028677 nonn
%O A028677 0,2
%A A028677 _Olivier Gérard_