299537288domain: NAppears in sequencesa(n+1) - 3*a(n) + a(n-1) = (2/3)(1+w^(n+1)+w^(2n+2)), where w = exp(2 Pi I / 3).at n=21A071618Number of circular binary sequences of length n with an odd number of 0's and no consecutive 1's.at n=41A366043