A bisection of A002083.

Terms

a(0) =1a(1) =1a(2) =3a(3) =11a(4) =42a(5) =165a(6) =654a(7) =2605a(8) =10398a(9) =41550a(10) =166116a(11) =664299a(12) =2656866a(13) =10626810a(14) =42505932a(15) =170021123a(16) =680079282a(17) =2720306730a(18) =10881206124a(19) =43524782946a(20) =174099048684a(21) =696396028620