Odd numbers in which parity of digits alternates.

Terms

a(0) =1a(1) =3a(2) =5a(3) =7a(4) =9a(5) =21a(6) =23a(7) =25a(8) =27a(9) =29a(10) =41a(11) =43a(12) =45a(13) =47a(14) =49a(15) =61a(16) =63a(17) =65a(18) =67a(19) =69a(20) =81a(21) =83a(22) =85a(23) =87a(24) =89a(25) =101a(26) =103a(27) =105a(28) =107a(29) =109