A172209 Numbers n such that 18n - 5 and 18n + 5 are primes.

1, 2, 6, 8, 9, 13, 16, 19, 21, 23, 28, 34, 36, 41, 42, 44, 49, 54, 57, 58, 61, 72, 78, 82, 83, 86, 89, 96, 99, 104, 111, 113, 132, 133, 149, 152, 154, 167, 173, 177, 187, 201, 211, 218, 236, 237, 247, 251, 258, 266, 273, 278, 288, 296, 302, 307, 314, 316, 317, 322

Offset

1,2

Links

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

Example

a(1)=1 because 18*1-5=13 is prime and 18*1+5=23 is prime.

Mathematica

Select[Range[400], AllTrue[18#+{5, -5}, PrimeQ]&] (* Harvey P. Dale, Feb 25 2022 *)

Prog

(Magma) [n: n in [1..2500]|IsPrime(18*n-5) and IsPrime(18*n+5)] // Vincenzo Librandi, Dec 19 2010
(PARI) forprime(p=2, 1e4, if(p%18==5 & isprime(p-10), print1(p\18", "))) \\ Charles R Greathouse IV, May 25 2011

Crossrefs

Cf. A000040, A172147, A172154.

Sequence in context: A034591 A047278 A242204 * A107737 A045138 A067704

Adjacent sequences: A172206 A172207 A172208 * A172210 A172211 A172212

Keyword

nonn,easy

Author

Juri-Stepan Gerasimov, Jan 29 2010

Extensions

Definition corrected and 49 inserted by R. J. Mathar and D. S. McNeil, May 22 2010

Corrected by D. S. McNeil, May 22 2010

Status

approved