A032620 Numbers k such that k concatenated with k+5 is a prime.

12, 16, 18, 28, 46, 64, 76, 78, 82, 88, 102, 126, 132, 138, 148, 154, 178, 184, 186, 196, 208, 214, 226, 228, 234, 246, 264, 282, 288, 298, 316, 318, 322, 324, 328, 342, 348, 352, 372, 408, 418, 424, 432, 438, 442, 444, 456, 462, 468, 472, 474, 478, 484

Offset: 1

Author

Patrick De Geest, May 15 1998

Keywords

• nonn
• base

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A032610.

Programs

Maple

filter:= n -> isprime(n * 10^(1+ilog10(n+5)) + n + 5):
select(filter, [seq(i,i=2..1000,2)]); # Robert Israel, May 13 2025

Mathematica

nc5pQ[n_]:=PrimeQ[FromDigits[Join[IntegerDigits[n],IntegerDigits[n+5]]]]; Select[Range[500],nc5pQ] (* Harvey P. Dale, Mar 25 2016 *)