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 A003938 #19 Jun 23 2025 02:46:29
%S A003938 720,25920,979200,4680000,138297600,1056706560,1721606400,12860654400,
%T A003938 68518981440,1095199948800,1004497044480,3057017889600,20674026236160,
%U A003938 47607300000000,102804157834560,210103196385600
%N A003938 Order of (usually) simple Chevalley group B_2(q), q = prime power.
%D A003938 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 A003938 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 A003938 <a href="/index/Gre#groups">Index entries for sequences related to groups</a>.
%F A003938 a(n) = b(A000961(n + 1), 2) where b(q,n) is defined in A003927. - _Sean A. Irvine_, Sep 22 2015
%t A003938 b[q_, n_] := q^(n^2) * Product[q^(2*k) - 1, {k, 1, n}] / GCD[2, q-1]; Table[b[q, 2], {q, Select[Range[30], PrimePowerQ]}] (* _Amiram Eldar_, Jun 23 2025 *)
%Y A003938 Cf. A000961, A003927, A003939, A003940, A003941, A003942.
%K A003938 nonn,easy
%O A003938 1,1
%A A003938 _N. J. A. Sloane_