Position of n-th 3 in A031324.

Terms

a(0) =3a(1) =7a(2) =10a(3) =20a(4) =21a(5) =22a(6) =64a(7) =75a(8) =77a(9) =84a(10) =97a(11) =103a(12) =113a(13) =116a(14) =140a(15) =142a(16) =153a(17) =162a(18) =172a(19) =173a(20) =197a(21) =198a(22) =203a(23) =212a(24) =213a(25) =216a(26) =220a(27) =226a(28) =228a(29) =233