Reversion of g.f. (beginning with x term) for number of trees with n nodes.

Terms

a(0) =1a(1) =-1a(2) =1a(3) =-2a(4) =5a(5) =-13a(6) =35a(7) =-98a(8) =282a(9) =-832a(10) =2505a(11) =-7662a(12) =23715a(13) =-74104a(14) =233429a(15) =-740511a(16) =2363816a(17) =-7587409a(18) =24473880a(19) =-79289278a(20) =257890856a(21) =-841789791a(22) =2756618710a(23) =-9053837032a(24) =29817032534a(25) =-98441372386a(26) =325753459625