a(n) is the smallest number that has exactly n binary palindrome divisors (A006995).

Terms

a(0) =1a(1) =3a(2) =9a(3) =15a(4) =99a(5) =45a(6) =135a(7) =189a(8) =315a(9) =495a(10) =945a(11) =765a(12) =2079a(13) =6237a(14) =3465a(15) =5355a(16) =4095a(17) =8415a(18) =31185a(19) =20475a(20) =25245a(21) =12285a(22) =85995a(23) =58905a(24) =61425a(25) =45045a(26) =69615a(27) =176715a(28) =446985a(29) =225225