A032705 Numbers n such that n prefixed by '5' and followed by '1' is prime.

2, 4, 7, 10, 17, 23, 26, 28, 35, 38, 43, 44, 47, 50, 52, 53, 58, 59, 64, 65, 70, 71, 74, 79, 80, 82, 85, 86, 88, 98, 100, 103, 106, 107, 113, 115, 124, 134, 136, 142, 143, 146, 148, 151, 152, 155, 158, 163, 169, 172, 187, 194, 197, 199, 202, 205, 208, 212