1131900domain: NAppears in sequencesE.g.f. exp(exp(1/2*x^2+1/6*x^3)-1).at n=11A191424Number of 4-good trees with n nodes.at n=9A292748a(n) = Product_{d|n} A019565(phi(d)), where phi is Euler totient function A000010.at n=51A332824