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%I #8 Jun 23 2013 09:08:53
%S 3,648,12597120,20056328248320,2589682730460637593600,
%T 27088537289801063207068178841600,
%U 22951765904242357263319251737033603284992000,1575188025865853631043462731239785102397842258177032192000,8756565436081269687990149660909266003169595871730647160978999995269120000
%N 3^(n^2+2n+1)*Product_{j=1..n} (9^j-1).
%C 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 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.
%t Table[3^(n^2+2n+1) Product[9^j-1,{j,n}],{n,0,10}] (* _Harvey P. Dale_, Jun 23 2013 *)
%Y Cf. A001309, A003956.
%Y 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 nonn
%O 0,1
%A _N. J. A. Sloane_, Feb 10 2004