A236554 - OEIS

%I #14 Feb 01 2014 09:01:56

%S 8,64,288,1056,4128,16416,65568,262176

%N Number of involutions in the quaternion ring over Z/(2^n)Z with i^2=j^2=1.

%F a(n) = A236553(2^n).

%t invo11[n_] :=  Length@Reduce[a^2 - b^2 + c^2 + d^2 ==1 && 2 a b== 0 && 2 a c == 0 && 2 a  d == 0, Modulus -> n];Table[invo11[2^n],{n,8}]

%Y Cf. A236553, A227867.

%K nonn,more,hard

%O 1,1

%A _José María Grau Ribas_, Jan 28 2014