Number of perfect powers (A001597) not exceeding 2^n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =5a(5) =8a(6) =11a(7) =16a(8) =23a(9) =31a(10) =42a(11) =58a(12) =82a(13) =114a(14) =156a(15) =217a(16) =299a(17) =417a(18) =583a(19) =814a(20) =1136a(21) =1589a(22) =2224a(23) =3116a(24) =4369a(25) =6136a(26) =8623a(27) =12128a(28) =17064a(29) =24023