a(0)=1; a(n) = Sum_{k=1..n-1} d(k)*a(n-k), where d(m) is m-th bit in binary expansion of n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =2a(5) =3a(6) =5a(7) =10a(8) =10a(9) =13a(10) =23a(11) =43a(12) =66a(13) =122a(14) =231a(15) =462a(16) =462a(17) =528a(18) =759a(19) =1452a(20) =1980a(21) =3201a(22) =5412a(23) =9603a(24) =15015a(25) =26598a(26) =47025a(27) =88638a(28) =162261a(29) =312939