A047825 Becomes prime after exactly 6 iterations of f(x) = sum of prime factors of x.

393, 889, 1142, 1179, 1257, 1270, 1285, 1315, 1389, 1502, 1542, 1563, 1578, 1838, 2217, 2284, 2305, 2326, 2474, 2540, 2761, 2766, 2787, 2827, 2913, 3004, 3084, 3156, 3193, 3207, 3505, 3507, 3537, 3589, 3676, 3771, 3826, 3873, 3957, 4006, 4167, 4195