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 A003921 #18 Jul 10 2025 04:17:07 %S A003921 60,979200,4106059776000,4408780839651901440000, %T A003921 1211875293642881119668928512000000, %U A003921 85278137430613949474674174708223909560320000000 %N A003921 Order of universal Chevalley group B_n (4). %D A003921 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 A003921 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 A003921 <a href="/index/Gre#groups">Index entries for sequences related to groups</a>. %F A003921 a(n) = B(4,n) where B(q,n) is defined in A003920. - _Sean A. Irvine_, Sep 22 2015 %F A003921 a(n) ~ c * 4^(2*n^2+n), where c = Product_{k>=1} (1-1/16^k) = 0.933594707399... . - _Amiram Eldar_, Jul 09 2025 %t A003921 B[q_, n_] := q^(n^2) * Product[q^(2*k) - 1, {k, 1, n}]; Table[B[4, n], {n, 1, 6}] (* _Amiram Eldar_, Jun 23 2025 *) %Y A003921 Cf. A003920, A003922, A003924, A003925, A003926. %K A003921 nonn,easy %O A003921 1,1 %A A003921 _N. J. A. Sloane_