20437401600domain: NAppears in sequencesa(n) = n! * C(n+2, 2) * 2^(n+1).at n=9A014297Expansion of e.g.f. x*(1-x)/(1-2*x).at n=11A052564E.g.f. x^2*(1+x-2x^2)/(1-2x).at n=11A052638