Position of n-th 2 in A031087.

Terms

a(0) =2a(1) =13a(2) =28a(3) =30a(4) =31a(5) =32a(6) =34a(7) =36a(8) =38a(9) =40a(10) =42a(11) =44a(12) =49a(13) =67a(14) =85a(15) =103a(16) =121a(17) =139a(18) =159a(19) =186a(20) =208a(21) =211a(22) =213a(23) =214a(24) =217a(25) =220a(26) =223a(27) =226a(28) =229a(29) =232