A239732 Primes p such that 2p+9 and 9p+2 are both prime.

5, 11, 19, 29, 31, 71, 101, 109, 131, 151, 179, 211, 229, 239, 269, 281, 311, 491, 521, 541, 719, 739, 751, 809, 919, 929, 971, 1051, 1061, 1129, 1181, 1291, 1361, 1439, 1481, 1621, 1741, 1811, 1831, 2111, 2131, 2221, 2371, 2389, 2411, 2521, 2539, 2549, 2689, 2791

Offset

1,1

Comments

All of the numbers in this sequence, except a(1), are either 1 or 9 mod 10.

Links

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

Example

5 is prime, 2*5+9 = 19 is prime, and 9*5+2 = 47 is prime. Thus, 5 is a member of this sequence.

Mathematica

Select[Prime[Range[500]], And@@PrimeQ[{2#+9, 9#+2}]&] (* Harvey P. Dale, Apr 23 2014 *)

Prog

(Python)
import sympy
from sympy import isprime
{print(n) for n in range(5000) if isprime(2*n+9) and isprime(9*n+2) and isprime(n)}
(PARI) s=[]; forprime(p=2, 3000, if(isprime(2*p+9) && isprime(9*p+2), s=concat(s, p))); s \\ Colin Barker, Mar 26 2014

Crossrefs

Sequence in context: A275068 A038872 A141158 * A130828 A244241 A108151

Adjacent sequences: A239729 A239730 A239731 * A239733 A239734 A239735

Keyword

nonn,easy

Author

Derek Orr, Mar 25 2014

Status

approved