Position of n-th 2 in A031235.

Terms

a(0) =2a(1) =9a(2) =16a(3) =18a(4) =19a(5) =20a(6) =22a(7) =24a(8) =29a(9) =39a(10) =51a(11) =66a(12) =76a(13) =79a(14) =81a(15) =82a(16) =85a(17) =88a(18) =96a(19) =111a(20) =122a(21) =125a(22) =126a(23) =128a(24) =131a(25) =134a(26) =137a(27) =140a(28) =141a(29) =143