For n>0, a(n) = least positive number m such that 8^m == +1 or -1 (mod 2n + 1), with a(0) = 0 by convention.

A003570

For n>0, a(n) = least positive number m such that 8^m == +1 or -1 (mod 2n + 1), with a(0) = 0 by convention.