A026190 a(n) = (1/2)*s(n), where s(n) is the n-th even number in A026142.

2, 1, 4, 6, 7, 3, 10, 12, 13, 5, 16, 18, 19, 21, 22, 8, 25, 9, 28, 30, 31, 11, 34, 36, 37, 39, 40, 14, 43, 15, 46, 48, 49, 17, 52, 54, 55, 57, 58, 20, 61, 63, 64, 66, 67, 23, 70, 24, 73, 75, 76, 26, 79, 27, 82, 84, 85, 29, 88, 90, 91, 93, 94