a(n) is the number of prime powers k such that ceiling(log_2(k)) = n.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =8a(5) =9a(6) =17a(7) =26a(8) =47a(9) =81a(10) =142a(11) =264a(12) =474a(13) =883a(14) =1629a(15) =3045a(16) =5735a(17) =10780a(18) =20429a(19) =38688a(20) =73654a(21) =140426a(22) =268341a(23) =513867a(24) =986034a(25) =1894410a(26) =3646135a(27) =7027826a(28) =13562626a(29) =26208249