A103935 Choose a(n) to be the smallest odd number not yet used such that: a(1) = 1, a(2n) = composite, a(2n+1) = prime and partial sums are alternately composite or prime.

1, 9, 3, 15, 13, 21, 5, 25, 11, 27, 7, 33, 23, 35, 29, 39, 17, 45, 31, 49, 19, 51, 61, 55, 37, 57, 43, 63, 53, 65, 41, 69, 71, 75, 79, 77, 73, 81, 59, 85, 47, 87, 103, 91, 83, 93, 113, 95, 109, 99, 127, 105, 149, 111, 139, 115, 89, 117, 107, 119, 97, 121, 131, 123, 67, 125