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A023237 Numbers k such that k and 10*k + 1 are both prime. 7
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Primes which with a 1 appended stay prime.

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

Solutions of the equation (10*n+1)'+n'=2, where n' is the arithmetic derivative of n. - Paolo P. Lava, Oct 31 2012

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

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Last modified October 26 22:19 EDT 2021. Contains 348269 sequences. (Running on oeis4.)