G.f. A(x) satisfies: A(x) = 1 - Sum_{k=1..3} (x * A(x))^k.

Terms

a(0) =1a(1) =-1a(2) =0a(3) =1a(4) =1a(5) =-6a(6) =4a(7) =13a(8) =-13a(9) =-61a(10) =124a(11) =120a(12) =-516a(13) =-352a(14) =2848a(15) =-923a(16) =-11337a(17) =10165a(18) =49352a(19) =-88655a(20) =-159903a(21) =512430a(22) =450812a(23) =-2873276a(24) =-11660a(25) =13752804a(26) =-9160464a(27) =-62238760a(28) =91526344a(29) =239932224