Reversion of x - x^2 - x^3 - x^4.

Terms

a(0) =0a(1) =1a(2) =1a(3) =3a(4) =11a(5) =44a(6) =189a(7) =850a(8) =3951a(9) =18832a(10) =91542a(11) =452075a(12) =2261753a(13) =11439372a(14) =58394014a(15) =300455892a(16) =1556636807a(17) =8113709916a(18) =42518000652a(19) =223868503324