G.f.: Sum_{k>=0} A000041(k)^2 * x^k / Sum_{k>=0} A000009(k) * x^k.

Terms

a(0) =1a(1) =0a(2) =3a(3) =4a(4) =16a(5) =20a(6) =67a(7) =84a(8) =231a(9) =324a(10) =735a(11) =1026a(12) =2265a(13) =3086a(14) =6199a(15) =8880a(16) =16564a(17) =23390a(18) =42378a(19) =59496a(20) =103588a(21) =146376a(22) =244278a(23) =344186a(24) =564013a(25) =788168a(26) =1255201a(27) =1758400a(28) =2738833a(29) =3812242