A080065 Numbers n such that n == 3 modulo (spf(n)+1), where spf(m) is the smallest prime dividing m (A020639).

3, 15, 27, 39, 51, 63, 75, 87, 91, 99, 111, 123, 135, 147, 159, 171, 183, 195, 203, 207, 219, 231, 243, 255, 259, 267, 279, 291, 303, 315, 327, 339, 351, 363, 371, 375, 387, 399, 411, 423, 427, 435, 447, 459, 471, 483, 495, 507, 519, 531, 539, 543, 555, 567