Position of n-th 3 in A007376.

Terms

a(0) =3a(1) =17a(2) =37a(3) =50a(4) =52a(5) =54a(6) =56a(7) =57a(8) =58a(9) =60a(10) =62a(11) =64a(12) =66a(13) =68a(14) =77a(15) =97a(16) =117a(17) =137a(18) =157a(19) =177a(20) =201a(21) =231a(22) =261a(23) =281a(24) =284a(25) =287a(26) =290a(27) =291a(28) =293a(29) =296