Odd numbers written backwards.

Terms

a(0) =1a(1) =3a(2) =5a(3) =7a(4) =9a(5) =11a(6) =31a(7) =51a(8) =71a(9) =91a(10) =12a(11) =32a(12) =52a(13) =72a(14) =92a(15) =13a(16) =33a(17) =53a(18) =73a(19) =93a(20) =14a(21) =34a(22) =54a(23) =74a(24) =94a(25) =15a(26) =35a(27) =55a(28) =75a(29) =95