a(n) is the number k such that 2^(2k+1)-1 = A000668(n+1).

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =8a(5) =9a(6) =15a(7) =30a(8) =44a(9) =53a(10) =63a(11) =260a(12) =303a(13) =639a(14) =1101a(15) =1140a(16) =1608a(17) =2126a(18) =2211a(19) =4844a(20) =4970a(21) =5606a(22) =9968a(23) =10850a(24) =11604a(25) =22248a(26) =43121a(27) =55251a(28) =66024a(29) =108045