a(n) = 4*n + 1.

Terms

a(0) =1a(1) =5a(2) =9a(3) =13a(4) =17a(5) =21a(6) =25a(7) =29a(8) =33a(9) =37a(10) =41a(11) =45a(12) =49a(13) =53a(14) =57a(15) =61a(16) =65a(17) =69a(18) =73a(19) =77a(20) =81a(21) =85a(22) =89a(23) =93a(24) =97a(25) =101a(26) =105a(27) =109a(28) =113a(29) =117