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 A028681 #15 Jul 12 2025 08:33:55
%S A028681 1,342,44446320,2090711424299040,35507456811518119000588800,
%T A028681 217698482437446717711443628892666137600,
%U A028681 481835288795046555242155407852974930874821656470528000,384989616762670041552999657317996225002975219911214265653201810077696000
%N A028681 Galois numbers for p=19; order of group AGL(n,19).
%H A028681 Vincenzo Librandi, <a href="/A028681/b028681.txt">Table of n, a(n) for n = 0..27</a>
%H A028681 <a href="/index/Gre#groups">Index entries for sequences related to groups</a>.
%F A028681 a(n) = 19^n * Product_{k=0..n-1} (19^n - 19^k).
%F A028681 a(n) ~ c * 19^(n^2+n), where c = Product_{k>=1} (1 - 1/19^k) = 0.944598742929... . - _Amiram Eldar_, Jul 12 2025
%t A028681 FoldList[ #1*19^#2 (19^#2-1)&, 1, Range[ 20 ] ]
%t A028681 a[n_] := 19^n * Product[19^n - 19^k, {k, 0, n-1}]; Array[a, 10, 0] (* _Amiram Eldar_, Jul 12 2025 *)
%o A028681 (PARI) a(n) = 19^n * prod(k = 0, n-1, 19^n - 19^k); \\ _Amiram Eldar_, Jul 12 2025
%Y A028681 Cf. A028365, A028665, A028667, A028669, A028673, A028675, A028679, A028685.
%K A028681 nonn
%O A028681 0,2
%A A028681 _Olivier Gérard_