Position of n-th 2 in A030998.

Terms

a(0) =2a(1) =12a(2) =21a(3) =23a(4) =25a(5) =26a(6) =27a(7) =29a(8) =31a(9) =33a(10) =40a(11) =54a(12) =68a(13) =82a(14) =99a(15) =120a(16) =134a(17) =137a(18) =140a(19) =141a(20) =143a(21) =146a(22) =149a(23) =152a(24) =162a(25) =183a(26) =204a(27) =225a(28) =238a(29) =241