A285805 Prime numbers p such that 6*p-1 and 6*p+1 are composite numbers.

31, 41, 71, 79, 89, 97, 139, 149, 167, 179, 191, 193, 211, 223, 251, 281, 307, 337, 349, 353, 401, 409, 419, 421, 431, 433, 479, 487, 491, 499, 509, 521, 541, 547, 563, 571, 587, 619, 631, 643, 659, 673, 677, 691, 701, 719, 739, 757, 769, 809

Offset: 1

Author

Dimitris Valianatos, Apr 26 2017

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A060212, A099047.

Programs

Maple

filter:= n -> isprime(n) and not isprime(6*n-1) and not isprime(6*n+1):
select(filter, [seq(i,i=3..1000,2)]); # Robert Israel, Jan 05 2020

Mathematica

Select[Prime@Range@150, ! PrimeQ[6 # - 1] && ! PrimeQ[6 # + 1] &] (* Robert G. Wilson v, Apr 27 2017 *)
Select[Prime[Range[150]],NoneTrue[6#+{1,-1},PrimeQ]&] (* Harvey P. Dale, Jun 10 2022 *)

PARI

{forprime(n=3, 1000, if(!isprime(6*n-1)&&!isprime(6*n+1), print1(n", ")))}