G.f. satisfies A(x) = 1 + x*(1 + x*A(x)^6)^3.

Terms

a(0) =1a(1) =1a(2) =3a(3) =21a(4) =136a(5) =1032a(6) =8139a(7) =66975a(8) =567417a(9) =4915386a(10) =43350639a(11) =387889254a(12) =3512655498a(13) =32133132074a(14) =296496163113