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5^(n^2+2n+1)*Product_{j=1..n} (25^j-1).
7

%I #7 Oct 04 2012 10:28:48

%S 5,15000,29250000000,35703281250000000000,

%T 27239372138671875000000000000000,

%U 12988743471794208526611328125000000000000000000,3870947187719439049405530095100402832031250000000000000000000000,721020100095350865678782984846420731628313660621643066406250000000000000000000000000

%N 5^(n^2+2n+1)*Product_{j=1..n} (25^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.

%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