A032668 Digit '5' concatenated with a(n) is a prime.

3, 9, 21, 23, 41, 47, 57, 63, 69, 71, 77, 87, 93, 99, 101, 107, 113, 119, 147, 153, 167, 171, 179, 189, 197, 209, 227, 231, 233, 237, 261, 273, 279, 281, 297, 303, 309, 323, 333, 347, 351, 381, 387, 393, 399, 407, 413, 417, 419, 431, 437, 441

Offset: 1

Author

Patrick De Geest, May 15 1998

Keywords

• nonn
• base

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..10000

Programs

Mathematica

Select[Range[500],PrimeQ[FromDigits[Join[{5},IntegerDigits[#]]]]&] (* Harvey P. Dale, Mar 23 2012 *)