Position of n-th 3 in A030567.

Terms

a(0) =3a(1) =12a(2) =24a(3) =31a(4) =33a(5) =35a(6) =36a(7) =37a(8) =39a(9) =41a(10) =48a(11) =60a(12) =75a(13) =93a(14) =111a(15) =121a(16) =124a(17) =127a(18) =129a(19) =130a(20) =133a(21) =136a(22) =147a(23) =165a(24) =183a(25) =201a(26) =219a(27) =229a(28) =232a(29) =235