A032715 n prefixed by '7' and followed by '3' is a prime.

3, 4, 7, 10, 19, 21, 24, 25, 28, 33, 39, 43, 52, 57, 58, 60, 64, 67, 70, 72, 75, 79, 82, 85, 87, 88, 93, 96, 99, 102, 114, 115, 123, 126, 129, 133, 135, 136, 141, 144, 145, 147, 148, 150, 156, 159, 163, 166, 169, 171, 184, 193, 196, 198, 199, 204, 205, 207