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A199717 Numbers n such that 6*n-1 is composite, but 6*n-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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

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 * A068308 A163871 A201915

Adjacent sequences:  A199714 A199715 A199716 * A199718 A199719 A199720

KEYWORD

nonn,easy

AUTHOR

Eleonora Echeverri-Toro, Nov 09 2011

STATUS

approved

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Last modified July 31 08:38 EDT 2021. Contains 346369 sequences. (Running on oeis4.)