A032726 Numbers k such that k prefixed by '1' and followed by '9' is a prime.

0, 3, 4, 7, 9, 10, 12, 22, 24, 25, 27, 28, 31, 39, 40, 42, 43, 45, 48, 49, 54, 55, 57, 60, 61, 66, 69, 70, 75, 78, 87, 88, 94, 97, 99, 105, 106, 111, 114, 115, 123, 127, 129, 132, 136, 139, 148, 151, 154, 157, 168, 169, 171, 177, 178, 183, 190, 193, 195, 196, 204

Offset: 1

Author

Patrick De Geest, May 15 1998

Keywords

• nonn
• base

Programs

Mathematica

Select[Range[0,200],PrimeQ@FromDigits[Join[{1},IntegerDigits@#,{9}]]&] (* Giorgos Kalogeropoulos, Jul 28 2021 *)