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A199717
Numbers k such that 6*k-1 is composite, but 6*k-5 is prime.
1
6, 11, 13, 24, 26, 27, 31, 34, 36, 41, 46, 48, 56, 57, 62, 63, 69, 71, 73, 88, 91, 92, 96, 97, 101, 102, 104, 106, 111, 116, 119, 122, 123, 126, 132, 136, 139, 154, 166, 167, 171, 173, 174, 176, 178, 179, 187, 188, 189, 193, 196, 201, 206, 207, 209, 216, 221
OFFSET
1,1
LINKS
MATHEMATICA
Select[Range[221], PrimeQ[6 # - 5] && ! PrimeQ[6 # - 1] &] (* T. D. Noe, Nov 09 2011 *)
PROG
(Magma) [ p div 6 +1: p in PrimesUpTo(1326) | not IsPrime(p+4) and p mod 6 eq 1 ]; // Bruno Berselli, Nov 09 2011
(PARI) is(n)=isprime(6*n-5) && !isprime(6*n-1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Cf. A186243.
Sequence in context: A315372 A315373 A154293 * A163871 A201915 A237606
KEYWORD
nonn,easy
AUTHOR
STATUS
approved