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A023224 Numbers n such that n and 7n + 4 are both prime. 3
7, 19, 37, 61, 79, 97, 139, 151, 157, 211, 229, 271, 307, 349, 379, 457, 487, 547, 571, 601, 607, 619, 631, 709, 751, 757, 769, 829, 877, 907, 937, 997, 1021, 1069, 1117, 1129, 1237, 1249, 1291, 1327, 1429, 1447, 1471, 1489, 1549, 1567, 1579, 1621, 1627, 1699 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Subsequence of A024902. All terms are congruent to 1 mod 6 because 7(6n+5)+4 is divisible by 3. - John Cerkan, Jul 08 2016

LINKS

John Cerkan, Table of n, a(n) for n = 1..10000

MAPLE

A023224:=n->`if`(isprime(n) and isprime(7*n+4), n, NULL): seq(A023224(n), n=1..5000); # Wesley Ivan Hurt, Jul 08 2016

MATHEMATICA

lst={}; Do[p=Prime[n]; If[PrimeQ[7*p+4], AppendTo[lst, p]], {n, 6!}]; lst (* Vladimir Joseph Stephan Orlovsky, Aug 16 2009 *)

PROG

(MAGMA) [n: n in [0..100000] | IsPrime(n) and IsPrime(7*n+4)] // Vincenzo Librandi, Nov 19 2010

(PARI) lista(nn) = for(p=2, nn, if(isprime(7*p+4), print1(p, ", "))); \\ Altug Alkan, Jul 08 2016

CROSSREFS

Cf. A024902.

Sequence in context: A130056 A136057 A177092 * A113743 A003215 A133323

Adjacent sequences:  A023221 A023222 A023223 * A023225 A023226 A023227

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified September 25 12:56 EDT 2017. Contains 292469 sequences.