a(n) = number of pairs {x,y} with (x,y > 1) such that x^y (= terms of A072103) has bit length n.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =4a(5) =3a(6) =8a(7) =7a(8) =10a(9) =15a(10) =19a(11) =25a(12) =38a(13) =46a(14) =66a(15) =90a(16) =126a(17) =169a(18) =240a(19) =332a(20) =467a(21) =646a(22) =909a(23) =1270a(24) =1787a(25) =2513a(26) =3529a(27) =4966a(28) =6998a(29) =9853