G.f. A(x) satisfies A(x - A(x)) = x^3 + x^4.

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =25a(5) =78a(6) =303a(7) =1104a(8) =4536a(9) =18174a(10) =78042a(11) =333204a(12) =1484446a(13) =6635245a(14) =30501324a(15) =141223812a(16) =666998868a(17) =3177455112a(18) =15366908520a(19) =74979351720a(20) =370318109661