Number of odd squarefree numbers <= 2^n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =7a(5) =13a(6) =26a(7) =52a(8) =105a(9) =209a(10) =415a(11) =830a(12) =1661a(13) =3321a(14) =6641a(15) =13279a(16) =26565a(17) =53123a(18) =106237a(19) =212488a(20) =424973a(21) =849945a(22) =1699889a(23) =3399761a(24) =6799540a(25) =13599124a(26) =27198203a(27) =54396423a(28) =108792774a(29) =217585510