91625794219domain: NAppears in sequencesComposite values of n such that 2^n == 2 (mod n*(n-1)).at n=0A217468a(n) = (1^n + (-2)^n + 4^n)/3.at n=19A245489a(n) = (q^2-q+1)/3 where q = 2^(2*n+1) = A004171(n).at n=9A345963