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

1,1

Links

Table of n, a(n) for n=1..8.

Formula

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

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}]

Crossrefs

Cf. A236553, A227867.

Sequence in context: A208143 A189265 A167239 * A173502 A223670 A189618

Adjacent sequences: A236551 A236552 A236553 * A236555 A236556 A236557

Keyword

nonn,more,hard

Author

José María Grau Ribas, Jan 28 2014

Status

approved