Number of cubefree integers not exceeding 2^n.

Terms

a(0) =1a(1) =2a(2) =4a(3) =7a(4) =14a(5) =27a(6) =54a(7) =107a(8) =214a(9) =427a(10) =854a(11) =1706a(12) =3410a(13) =6815a(14) =13629a(15) =27259a(16) =54521a(17) =109042a(18) =218080a(19) =436158a(20) =872318a(21) =1744638a(22) =3489278a(23) =6978546a(24) =13957092a(25) =27914186a(26) =55828364a(27) =111656716a(28) =223313428a(29) =446626866