G.f. A(x) satisfies A(x) = ( 1 + 9*x*A(x)/(1 - x) )^(1/3).

Terms

a(0) =1a(1) =3a(2) =3a(3) =-6a(4) =3a(5) =57a(6) =-141a(7) =-321a(8) =2460a(9) =-1572a(10) =-29400a(11) =92505a(12) =196905a(13) =-1841208a(14) =1608636a(15) =24028995a(16) =-85167204a(17) =-161127519a(18) =1756947801a(19) =-1901675715a(20) =-23476298442a(21) =91225005105a(22) =149447955855