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 A003839 #14 Jun 24 2025 11:03:35
%S A003839 3,28224,2317591180800,112554991177798901760000,
%T A003839 52386144472825139642572263782154240000,
%U A003839 14630778277213500974314928221817819519899234908241920000
%N A003839 Order of (usually) simple Chevalley group D_n (7).
%D A003839 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 A003839 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 A003839 <a href="/index/Gre#groups">Index entries for sequences related to groups</a>.
%F A003839 a(n) = d(7,n) where d(q,n) is defined in A003837. - _Sean A. Irvine_, Sep 17 2015
%t A003839 d[q_, n_] := q^(n*(n-1)) * (q^n-1) * Product[q^(2*k) - 1, {k, 1, n-1}] / GCD[4, q^n-1]; Table[d[7, n], {n, 1, 8}] (* _Amiram Eldar_, Jun 24 2025 *)
%Y A003839 Cf. A003837, A003838, A003840.
%K A003839 nonn,easy
%O A003839 1,1
%A A003839 _N. J. A. Sloane_