INVERT transform of A000055.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =17a(5) =36a(6) =78a(7) =170a(8) =375a(9) =833a(10) =1870a(11) =4229a(12) =9654a(13) =22223a(14) =51622a(15) =120961a(16) =286029a(17) =682398a(18) =1642821a(19) =3990231a(20) =9777678a(21) =24166327a(22) =60233185a(23) =151350709a(24) =383287499a(25) =977918150a(26) =2512805727a(27) =6500178867a(28) =16921248231a(29) =44310852884