Position of n-th 2 in A031007.

Terms

a(0) =2a(1) =11a(2) =22a(3) =24a(4) =25a(5) =26a(6) =28a(7) =30a(8) =32a(9) =34a(10) =39a(11) =53a(12) =67a(13) =81a(14) =97a(15) =118a(16) =134a(17) =137a(18) =139a(19) =140a(20) =143a(21) =146a(22) =149a(23) =152a(24) =160a(25) =181a(26) =202a(27) =223a(28) =240a(29) =243