Let k be the exponent of highest power of 2 dividing n (A007814); a(n) = 2^(k+1)-1.

Terms

a(0) =1a(1) =3a(2) =1a(3) =7a(4) =1a(5) =3a(6) =1a(7) =15a(8) =1a(9) =3a(10) =1a(11) =7a(12) =1a(13) =3a(14) =1a(15) =31a(16) =1a(17) =3a(18) =1a(19) =7a(20) =1a(21) =3a(22) =1a(23) =15a(24) =1a(25) =3a(26) =1a(27) =7a(28) =1a(29) =3