Leftmost column of triangle A136561.

Terms

a(0) =1a(1) =2a(2) =4a(3) =-5a(4) =13a(5) =-30a(6) =75a(7) =-200a(8) =524a(9) =-1299a(10) =3038a(11) =-6762a(12) =14482a(13) =-30162a(14) =61691a(15) =-124998a(16) =252744a(17) =-512805a(18) =1047661a(19) =-2158235a(20) =4481801a(21) =-9368303a(22) =19674518a(23) =-41437744a(24) =87399483a(25) =-184412912a(26) =388975790a(27) =-819684340a(28) =1724741941a(29) =-3621720214