Number of 4-almost primes f such that 2^n < f <= 2^(n+1).

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =1a(5) =5a(6) =7a(7) =20a(8) =37a(9) =81a(10) =173a(11) =344a(12) =736a(13) =1461a(14) =3065a(15) =6208a(16) =12643a(17) =25662a(18) =52014a(19) =105487a(20) =212566a(21) =430007a(22) =865650a(23) =1744136a(24) =3508335a(25) =7053390a(26) =14167804a(27) =28441899a(28) =57065447a(29) =114418462