Position of n-th 3 in A030386.

Terms

a(0) =3a(1) =10a(2) =18a(3) =21a(4) =23a(5) =25a(6) =26a(7) =27a(8) =37a(9) =49a(10) =61a(11) =65a(12) =68a(13) =71a(14) =73a(15) =74a(16) =85a(17) =97a(18) =109a(19) =113a(20) =116a(21) =119a(22) =121a(23) =122a(24) =126a(25) =129a(26) =132a(27) =133a(28) =135a(29) =138