a(n) is the number of numbers in the interval [2^(n-1), 2^n-1] that have exactly n divisors.

Terms

a(0) =1a(1) =2a(2) =1a(3) =4a(4) =1a(5) =6a(6) =1a(7) =25a(8) =3a(9) =10a(10) =1a(11) =212a(12) =1a(13) =27a(14) =8a(15) =3625a(16) =1a(17) =1291a(18) =1a(19) =7687a(20) =18a(21) =265a(22) =1a(23) =629369a(24) =4a(25) =885a(26) =695a(27) =365370a(28) =1a(29) =685360