A032722 Numbers k such that k prefixed by '5' and followed by '7' is prime.

4, 5, 7, 8, 10, 14, 16, 19, 22, 23, 29, 34, 38, 40, 41, 43, 47, 50, 52, 55, 64, 65, 71, 73, 80, 82, 85, 86, 89, 92, 98, 104, 113, 115, 119, 121, 125, 128, 130, 134, 140, 142, 143, 148, 151, 157, 160, 163, 164, 176, 178, 179, 181, 182, 190, 197, 202, 205, 206, 212

Offset: 1

Author

Patrick De Geest, May 15 1998

Keywords

• nonn
• base

Crossrefs

Cf. A032702-A032733.

Programs

Mathematica

Select[Range[250],PrimeQ[FromDigits[Join[{5},IntegerDigits[#], {7}]]]&] (* Harvey P. Dale, Jul 24 2011 *)

Extensions

Offset changed by Andrew Howroyd, Aug 13 2024