A023237 Numbers k such that k and 10*k + 1 are both prime.

3, 7, 13, 19, 31, 43, 97, 103, 109, 151, 157, 181, 193, 211, 241, 271, 337, 349, 367, 409, 421, 439, 487, 523, 547, 571, 601, 613, 631, 691, 733, 769, 811, 823, 829, 883, 937, 1009, 1021, 1033, 1039, 1063, 1069, 1117, 1201, 1249, 1279, 1291, 1459, 1483, 1489

Offset

1,1

Comments

Primes which with a 1 appended stay prime.

Corresponding values of 10n + 1 in A055781. - Jaroslav Krizek, Jul 14 2010

Subsequence of A024912. - Michel Marcus, May 21 2014

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Maple

with(numtheory); for i from 1 to 500 do if isprime(10*ithprime(i)+1) then printf(`%d, `, ithprime(i)) fi: od: # James A. Sellers, Apr 09 2005

Mathematica

Select[Prime[Range[ 240]], PrimeQ[FromDigits[Join[IntegerDigits[ # ], {1}]]] &] (* Robert G. Wilson v, Apr 09 2005 *)
Select[Prime[Range[900]], PrimeQ[10 # + 1] &] (* Vincenzo Librandi, May 21 2014 *)

Prog

(Magma) [n: n in [0..1000] | IsPrime(n) and IsPrime(10*n+1)] // Vincenzo Librandi, Nov 20 2010
(Magma) [p: p in PrimesUpTo(1100)| IsPrime(10*p+1)]; // Vincenzo Librandi, May 21 2014

Crossrefs

Cf. A024912, A055781, A105435.

Sequence in context: A271981 A103521 A103966 * A106061 A155703 A023217

Adjacent sequences: A023234 A023235 A023236 * A023238 A023239 A023240

Keyword

nonn,easy

Author

David W. Wilson

Extensions

Edited by N. J. A. Sloane at the suggestion of M. F. Hasler, Aug 24 2007

Status

approved