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A239733 Primes p such that 4p+9 and 9p+4 are both prime. 1
7, 11, 23, 37, 41, 67, 71, 97, 113, 137, 163, 191, 197, 263, 307, 317, 401, 421, 491, 617, 653, 683, 727, 823, 881, 883, 907, 947, 953, 967, 1031, 1087, 1103, 1217, 1231, 1297, 1451, 1493, 1523, 1567, 1693, 1747, 1933, 1973, 2053, 2141, 2207, 2221, 2281, 2293 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All numbers in this sequence are either 1, 3, or 7 mod 10.

LINKS

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

EXAMPLE

7 is prime, 4*7+9 = 37 is prime, and 9*7+4 = 67 is prime. Thus, 7 is a member of this sequence.

MATHEMATICA

Select[Prime[Range[400]], AllTrue[{4#+9, 9#+4}, PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Aug 26 2014 *)

PROG

(Python)

import sympy

from sympy import isprime

{print(n) for n in range(5000) if isprime(4*n+9) and isprime(9*n+4) and isprime(n)}

(PARI) s=[]; forprime(p=2, 3000, if(isprime(4*p+9) && isprime(9*p+4), s=concat(s, p))); s \\ Colin Barker, Mar 26 2014

CROSSREFS

Sequence in context: A255769 A175625 A082496 * A265768 A210001 A294074

Adjacent sequences:  A239730 A239731 A239732 * A239734 A239735 A239736

KEYWORD

nonn,easy

AUTHOR

Derek Orr, Mar 25 2014

STATUS

approved

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Last modified February 24 22:57 EST 2020. Contains 332216 sequences. (Running on oeis4.)