37566720domain: NAppears in sequencesa(n) = (1/16)*( binomial(4*n, 2*n) - (-1)^n*binomial(2*n, n) + (1-(-1)^n)*binomial(2*n, n)^2 ).at n=8A037980Number of orbits of length n under the map whose periodic points are counted by A000984.at n=15A060165