A023270 Primes that remain prime through 2 iterations of function f(x) = 10x + 9.

5, 13, 19, 23, 47, 61, 103, 127, 139, 233, 257, 293, 331, 433, 463, 491, 499, 547, 593, 701, 859, 967, 1009, 1013, 1049, 1223, 1321, 1399, 1493, 1567, 1723, 1811, 1867, 1889, 1997, 2039, 2063, 2087, 2137, 2203, 2267, 2273, 2309, 2423, 2437, 2441, 2609, 2633

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Comments

Primes p such that 10*p+9 and 100*p+99 are also primes. - Vincenzo Librandi, Aug 04 2010

Links

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

Programs

Magma

[n: n in [1..100000] | IsPrime(n) and IsPrime(10*n+9) and IsPrime(100*n+99)] // Vincenzo Librandi, Aug 04 2010

Mathematica

Select[Prime[Range[400]],AllTrue[NestList[10#+9&,#,2],PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Jun 05 2015 *)