Powers of primes. Alternatively, 1 and the prime powers (p^k, p prime, k >= 1).

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =7a(6) =8a(7) =9a(8) =11a(9) =13a(10) =16a(11) =17a(12) =19a(13) =23a(14) =25a(15) =27a(16) =29a(17) =31a(18) =32a(19) =37a(20) =41a(21) =43a(22) =47a(23) =49a(24) =53a(25) =59a(26) =61a(27) =64a(28) =67a(29) =71