Transform of A000027 by the T_{1,1} transformation (see link).

Terms

a(0) =2a(1) =6a(2) =15a(3) =35a(4) =81a(5) =188a(6) =437a(7) =1016a(8) =2362a(9) =5491a(10) =12765a(11) =29675a(12) =68986a(13) =160373a(14) =372822a(15) =866706a(16) =2014847a(17) =4683951a(18) =10888865a(19) =25313540a(20) =58846841a(21) =136802308a(22) =318026782a(23) =739322571a(24) =1718716457a(25) =3995531011a(26) =9288482690a(27) =21593102505a(28) =50197873146a(29) =116695897118