Position of n-th 3 in A031269.

Terms

a(0) =3a(1) =7a(2) =9a(3) =18a(4) =23a(5) =28a(6) =29a(7) =44a(8) =49a(9) =54a(10) =62a(11) =64a(12) =72a(13) =74a(14) =89a(15) =90a(16) =100a(17) =104a(18) =105a(19) =112a(20) =113a(21) =117a(22) =127a(23) =133a(24) =138a(25) =140a(26) =147a(27) =166a(28) =168a(29) =175