1985612310domain: NAppears in sequencesExpansion of (1+x^3*C^2)*C^2, where C = (1-(1-4*x)^(1/2))/(2*x) is g.f. for Catalan numbers, A000108.at n=18A071731a(n) = Catalan(n) * (n^2 + 2) / (n + 2).at n=17A344191