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

Terms

a(0) =1a(1) =1a(2) =0a(3) =1a(4) =3a(5) =3a(6) =4a(7) =15a(8) =30a(9) =42a(10) =99a(11) =255a(12) =475a(13) =915a(14) =2232a(15) =4977a(16) =9945a(17) =21945a(18) =51093a(19) =110634a(20) =238005a(21) =542341a(22) =1227390a(23) =2696841a(24) =6035886a(25) =13770402a(26) =31001133a(27) =69485295a(28) =157945293a(29) =359888373