Position of 2^n among the powers of primes (A000961).

Terms

a(0) =1a(1) =2a(2) =4a(3) =7a(4) =11a(5) =19a(6) =28a(7) =45a(8) =71a(9) =118a(10) =199a(11) =341a(12) =605a(13) =1079a(14) =1962a(15) =3591a(16) =6636a(17) =12371a(18) =23151a(19) =43580a(20) =82268a(21) =155922a(22) =296348a(23) =564689a(24) =1078556a(25) =2064590a(26) =3959000a(27) =7605135a(28) =14632961a(29) =28195587