G.f. A(x) satisfies: 1 - x = Sum_{n>=0} (x^(3*n) + (-1)^n*A(x))^n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =4a(5) =6a(6) =11a(7) =19a(8) =33a(9) =60a(10) =110a(11) =201a(12) =372a(13) =696a(14) =1305a(15) =2456a(16) =4654a(17) =8855a(18) =16896a(19) =32366a(20) =62217a(21) =119910a(22) =231704a(23) =448879a(24) =871531a(25) =1695541a(26) =3305057a(27) =6454033a(28) =12624041a(29) =24731009