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

1,1

Links

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

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 *)

Prog

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

Crossrefs

Cf. A060212, A099047.

Sequence in context: A381092 A060327 A202286 * A141180 A176371 A284531

Adjacent sequences: A285802 A285803 A285804 * A285806 A285807 A285808

Keyword

nonn

Author

Dimitris Valianatos, Apr 26 2017

Status

approved