Position of n-th 3 in A031045.

Terms

a(0) =3a(1) =14a(2) =30a(3) =41a(4) =43a(5) =45a(6) =46a(7) =47a(8) =49a(9) =51a(10) =53a(11) =55a(12) =62a(13) =78a(14) =94a(15) =110a(16) =129a(17) =153a(18) =177a(19) =193a(20) =196a(21) =199a(22) =201a(23) =202a(24) =205a(25) =208a(26) =211a(27) =214a(28) =225a(29) =249