Reversion of y - y^2 - y^3 + y^4 - y^5.

Terms

a(0) =0a(1) =1a(2) =1a(3) =3a(4) =9a(5) =33a(6) =126a(7) =510a(8) =2127a(9) =9113a(10) =39809a(11) =176735a(12) =794937a(13) =3615045a(14) =16593156a(15) =76773972a(16) =357692784a(17) =1676664234a(18) =7901590287a(19) =37416151209a(20) =177935914254a(21) =849461877990