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

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =10a(5) =29a(6) =86a(7) =266a(8) =842a(9) =2720a(10) =8924a(11) =29661a(12) =99654a(13) =337902a(14) =1154814a(15) =3973848a(16) =13756956a(17) =47878802a(18) =167425436a(19) =587954324a(20) =2072659700a(21) =7331934464a(22) =26018377112a(23) =92596633117a(24) =330415480966