G.f. A(x) satisfies A(x) = 1 + x*(1-x^3)^2*A(x)^3.

Terms

a(0) =1a(1) =1a(2) =3a(3) =12a(4) =53a(5) =261a(6) =1356a(7) =7313a(8) =40551a(9) =229719a(10) =1323727a(11) =7734705a(12) =45720966a(13) =272918624a(14) =1642803243a(15) =9960572367a(16) =60776178059a(17) =372912694665