G.f. satisfies: A(x) = 1 + x*A(x) + x^2*A(x)^4.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =20a(5) =72a(6) =273a(7) =1073a(8) =4333a(9) =17869a(10) =74937a(11) =318601a(12) =1370113a(13) =5949201a(14) =26046727a(15) =114857599a(16) =509669295a(17) =2274146599a(18) =10197234215a(19) =45925646367a(20) =207656685443a(21) =942302814363