A075066 Alternately odd and even composite numbers complementing the parity of the index.

9, 4, 15, 6, 21, 8, 25, 10, 27, 12, 33, 14, 35, 16, 39, 18, 45, 20, 49, 22, 51, 24, 55, 26, 57, 28, 63, 30, 65, 32, 69, 34, 75, 36, 77, 38, 81, 40, 85, 42, 87, 44, 91, 46, 93, 48, 95, 50, 99