A026252 a(n) = (1/2)*(s(n) + 1), where s(n) is the n-th odd number in A026250. Also a(n) = position of n in A026252.

2, 1, 7, 9, 12, 14, 3, 19, 4, 24, 26, 5, 31, 6, 36, 38, 41, 43, 8, 48, 50, 53, 55, 10, 60, 11, 65, 67, 70, 72, 13, 77, 79, 82, 84, 15, 89, 16, 94, 96, 17, 101, 18, 106, 108, 111, 113, 20, 118, 21, 123, 125, 22, 130, 23, 135, 137, 140, 142