Squarefree products of factors of Fermat numbers (A023394).

Terms

a(0) =1a(1) =3a(2) =5a(3) =15a(4) =17a(5) =51a(6) =85a(7) =255a(8) =257a(9) =641a(10) =771a(11) =1285a(12) =1923a(13) =3205a(14) =3855a(15) =4369a(16) =9615a(17) =10897a(18) =13107a(19) =21845a(20) =32691a(21) =54485a(22) =65535a(23) =65537a(24) =114689a(25) =163455a(26) =164737a(27) =196611a(28) =274177a(29) =319489