G.f. A(x) satisfies: A( A( x - x^2 ) ) = x + x^2.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =4a(5) =9a(6) =21a(7) =50a(8) =122a(9) =302a(10) =758a(11) =1928a(12) =4958a(13) =12849a(14) =33509a(15) =88122a(16) =233810a(17) =621022a(18) =1641150a(19) =4411180a(20) =12364368a(21) =33073210a(22) =71807506a(23) =206985492a(24) =1354944972a(25) =3153779248a(26) =-33794258600a(27) =-62697691948