A236554 Number of involutions in the quaternion ring over Z/(2^n)Z with i^2=j^2=1.

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

Offset: 1

Author

José María Grau Ribas, Jan 28 2014

Keywords

• nonn
• more
• hard

Crossrefs

Cf. A236553, A227867.

Programs

Mathematica

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}]

Formula

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