A032723 Numbers n such that n prefixed by '6' and followed by '7' is a prime.

0, 1, 4, 7, 19, 21, 24, 25, 27, 28, 31, 33, 36, 39, 42, 54, 57, 60, 63, 73, 82, 85, 90, 91, 94, 96, 97, 99, 100, 102, 105, 129, 135, 141, 148, 150, 154, 162, 163, 165, 166, 168, 171, 175, 183, 192, 196, 198, 201, 204, 205, 213, 220, 229, 232, 234, 241, 246, 247