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

Terms

a(0) =1a(1) =1a(2) =3a(3) =9a(4) =30a(5) =104a(6) =374a(7) =1380a(8) =5197a(9) =19893a(10) =77170a(11) =302716a(12) =1198729a(13) =4785455a(14) =19238706a(15) =77821522a(16) =316506253a(17) =1293489529a(18) =5309112257a(19) =21876225899a(20) =90459484106a(21) =375256749620