1111731933domain: NAppears in sequencesa(n) = 3*binomial(4*n-1, n-1)/(4*n-1).at n=11A006632a(3n+k) = (k+1)*binomial(4n+k, n)/(3n+k+1), where k is n reduced mod 3.at n=35A124753Expansion of g.f. A(x) satisfying A(x) = 1 + x*(3*A(x)^2 + A(-x)^2)/4.at n=23A369082