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 A001308 #15 Jul 08 2025 07:51:37
%S A001308 1,36,20160,174182400,23499295948800,50027557148216524800,
%T A001308 1691555775522928280469504000,911666827031785075278550369566720000,
%U A001308 7846393898179181843651374899795632943267840000
%N A001308 Order of Chevalley group D_n (2).
%D A001308 J. H. Conway, R. T. Curtis, S. P. Norton, R. A. Parker and R. A. Wilson, ATLAS of Finite Groups. Oxford Univ. Press, 1985 [for best online version see https://oeis.org/wiki/Welcome#Links_to_Other_Sites], p. xvi.
%D A001308 H. S. M. Coxeter and W. O. J. Moser, Generators and Relations for Discrete Groups, 4th ed., Springer-Verlag, NY, reprinted 1984, p. 131.
%H A001308 T. D. Noe, <a href="/A001308/b001308.txt">Table of n, a(n) for n = 1..20</a>
%H A001308 <a href="/index/Gre#groups">Index entries for sequences related to groups</a>.
%F A001308 a(n) = 2^(n*(n-1)) * (2^n - 1) * Product_{i=1..n-1} (2^(2*i) - 1).
%F A001308 a(n) ~ c * 2^(n*(2*n-1)), where c = A100221. - _Amiram Eldar_, Jul 07 2025
%p A001308 for m from 0 to 25 do N:=2^(m*(m-1))*mul( 4^i-1, i=1..m-1)*(2^m-1); lprint(N); od:
%t A001308 d[q_, n_] := q^(n*(n-1)) * (q^n-1) * Product[q^(2*k) - 1, {k, 1, n-1}]; Table[d[2, n], {n, 1, 9}] (* _Amiram Eldar_, Jul 07 2025 *)
%Y A001308 Cf. A003923, A100221.
%K A001308 nonn,easy
%O A001308 1,2
%A A001308 _N. J. A. Sloane_