Number of squarefree integers not exceeding 2^n.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =11a(5) =20a(6) =39a(7) =78a(8) =157a(9) =314a(10) =624a(11) =1245a(12) =2491a(13) =4982a(14) =9962a(15) =19920a(16) =39844a(17) =79688a(18) =159360a(19) =318725a(20) =637461a(21) =1274918a(22) =2549834a(23) =5099650a(24) =10199301a(25) =20398664a(26) =40797327a(27) =81594626a(28) =163189197a(29) =326378284