Halogen sequence: a(n) = A018227(n)-1.

Terms

a(0) =1a(1) =11a(2) =17a(3) =35a(4) =53a(5) =85a(6) =117a(7) =167a(8) =217a(9) =289a(10) =361a(11) =459a(12) =557a(13) =685a(14) =813a(15) =975a(16) =1137a(17) =1337a(18) =1537a(19) =1779a(20) =2021a(21) =2309a(22) =2597a(23) =2935a(24) =3273a(25) =3665a(26) =4057a(27) =4507a(28) =4957a(29) =5469