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A174101
Numbers k such that 2*k+1 and 6*k+1 are both primes of the form 6*m+1.
1
3, 6, 18, 21, 30, 33, 51, 63, 81, 90, 96, 105, 135, 138, 153, 156, 165, 168, 186, 216, 243, 261, 270, 300, 336, 363, 375, 378, 411, 426, 441, 453, 495, 510, 531, 543, 576, 585, 606, 615, 618, 648, 651, 723, 726, 741, 765, 798, 810, 828, 831, 846, 861, 891, 930
OFFSET
1,1
COMMENTS
All terms are divisible by 3. - Robert Israel, Jun 27 2024
LINKS
EXAMPLE
3 is a term: 3*2 + 1 = 7 and 3*6 + 1 = 19 are primes congruent to 1 (mod 6). - R. J. Mathar, Apr 16 2010
MAPLE
select(k -> isprime(2*k+1) and isprime(6*k+1), 3*[$1..1000]); # Robert Israel, Jun 27 2024
MATHEMATICA
Select[Range[1000], With[{c={2, 6}#+1}, AllTrue[c, PrimeQ]&&AllTrue[(c-1)/6, IntegerQ]&]] (* Harvey P. Dale, Aug 08 2022 *)
CROSSREFS
Sequence in context: A078318 A193433 A074370 * A088339 A064400 A352786
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from R. J. Mathar, Apr 16 2010
STATUS
approved