A141584 a(n) = the closest multiple of A053669(2n) to 2n. A053669(2n) = the smallest prime coprime to 2n.

3, 3, 5, 9, 9, 10, 15, 15, 20, 21, 21, 25, 27, 27, 28, 33, 33, 35, 39, 39, 40, 45, 45, 50, 51, 51, 55, 57, 57, 63, 63, 63, 65, 69, 69, 70, 75, 75, 80, 81, 81, 85, 87, 87, 91, 93, 93, 95, 99, 99, 100, 105, 105, 110, 111, 111, 115, 117, 117, 119, 123, 123, 125, 129, 129, 130