A032623 Numbers k such that k concatenated with k+8 is a prime.

1, 3, 13, 15, 21, 39, 49, 55, 69, 75, 91, 111, 115, 159, 163, 165, 169, 171, 183, 193, 195, 199, 201, 205, 211, 229, 235, 241, 249, 265, 271, 273, 289, 291, 309, 313, 319, 321, 325, 331, 333, 349, 351, 355, 363, 379, 381, 385, 391, 393, 405, 423, 441, 445

Offset: 1

Author

Patrick De Geest, May 15 1998

Keywords

• nonn
• base

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A032613.

Programs

Mathematica

Select[Range[500],PrimeQ[FromDigits[Flatten[IntegerDigits/@{#,#+8}]]]&] (* Harvey P. Dale, Nov 25 2023 *)