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A339582
Primes p = 8*r-1 such that all the prime factors of r are 7 mod 12.
1
7, 151, 631, 823, 1063, 1303, 1783, 2647, 2887, 3511, 4423, 4567, 4951, 5527, 6007, 6871, 7351, 7687, 7927, 8311, 9127, 10663, 11383, 11863, 12007, 12343, 12487, 13591, 14071, 15031, 15607, 15991, 16087, 17047, 17191, 17431, 17623, 17911, 19207, 20023, 20407
OFFSET
1,1
COMMENTS
Hugh Williams asks if this sequence is infinite.
LINKS
R. K. Guy, editor, Western Number Theory Problems, 1985-12-21 & 23, Typescript, Jul 13 1986, Dept. of Math. and Stat., Univ. Calgary, 11 pages. Annotated scan of pages 1, 3, 7, 9, with permission. See Problem 85:16.
MAPLE
filter:= n ->
isprime(n) and numtheory:-factorset((n+1)/8) mod 12 subset {7}:
select(filter, [seq(i, i=7..10^5, 8)]); # Robert Israel, Dec 24 2020
PROG
(PARI) isok(p) = if (isprime(p) && (Mod(p, 8)== -1), my(r=(p+1)/8, f=factor(r)[, 1]); #select(x->(Mod(x, 12) == 7), f) == #f); \\ Michel Marcus, Dec 24 2020
CROSSREFS
Subsequence of A007522.
Sequence in context: A329010 A309855 A364845 * A232446 A362491 A202558
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Dec 24 2020
EXTENSIONS
More terms from Michel Marcus, Dec 24 2020, who also added the initial term 7.
STATUS
approved