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 A090768 #11 Jul 07 2025 03:32:07
%S A090768 28,460992,18594942105600,1801630225452634420838400,
%T A090768 419114092659655895262507217606410240000,
%U A090768 234094442205343557204838431982679810784254737891983360000,313936710456644712932526713436974934772339799367593873556694922893983744000000,1010846620958915523772074873493863525346718205399610275113597795065777917926818948851860049494016000000
%N A090768 a(n) = 4*7^(n^2+2n+1)*Product_{j=1..n} (49^j-1).
%C A090768 The order of the p-Clifford group for an odd prime p is a*p^(n^2+2n+1)*Product_{j=1..n} (p^(2*j)-1), where a = gcd(p+1,4).
%H A090768 G. Nebe, E. M. Rains and N. J. A. Sloane, <a href="http://neilsloane.com/doc/cliff2.html">Self-Dual Codes and Invariant Theory</a>, Springer, Berlin, 2006.
%F A090768 From _Amiram Eldar_, Jul 07 2025: (Start)
%F A090768 a(n) = 4 * A090769(n).
%F A090768 a(n) ~ c * 7^(2*n^2+3*n+1), where c = 4 * Product_{k>=1} (1 - 1/7^(2*k)) = 3.916701388593... . (End)
%t A090768 a[n_] := 4*7^(n^2+2*n+1) * Product[49^j - 1, {j, 1, n}]; Array[a, 10, 0] (* _Amiram Eldar_, Jul 07 2025 *)
%Y A090768 Cf. A001309, A003956.
%Y A090768 Cf. A092299 and A092301 (p=3), A092300 and A089989 (p=5), A090768 and A090769 (p=7), A090770 (p=2, although this is the wrong formula in that case).
%K A090768 nonn
%O A090768 0,1
%A A090768 _N. J. A. Sloane_, Feb 10 2004