Position of n-th 2 in A031067.

Terms

a(0) =2a(1) =9a(2) =12a(3) =18a(4) =19a(5) =30a(6) =46a(7) =53a(8) =57a(9) =59a(10) =70a(11) =74a(12) =75a(13) =76a(14) =78a(15) =91a(16) =103a(17) =122a(18) =135a(19) =136a(20) =140a(21) =169a(22) =170a(23) =181a(24) =184a(25) =186a(26) =190a(27) =231a(28) =232a(29) =241