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 A143826 Numbers n such that 6n^2 - 1 is prime. 8
 1, 2, 3, 5, 7, 8, 10, 12, 13, 17, 20, 22, 27, 28, 30, 32, 35, 38, 43, 45, 52, 55, 58, 60, 62, 63, 65, 68, 70, 73, 75, 77, 82, 83, 87, 93, 97, 100, 102, 115, 120, 122, 130, 132, 143, 150, 153, 168, 173, 177, 187, 193, 197, 200, 207, 208, 210, 212, 220, 222, 223, 225 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS MATHEMATICA p = 6; a = {}; Do[k = p x^2 - 1; If[PrimeQ[k], AppendTo[a, x]], {x, 1, 1000}]; a Select[Range[250], PrimeQ[6#^2-1]&] (* Harvey P. Dale, Apr 22 2012 *) PROG (PARI) is(n)=isprime(6*n^2-1) \\ Charles R Greathouse IV, Feb 17 2017 CROSSREFS Cf. A090686. Sequence in context: A186344 A186317 A285077 * A001912 A186221 A083027 Adjacent sequences:  A143823 A143824 A143825 * A143827 A143828 A143829 KEYWORD nonn AUTHOR Artur Jasinski, Sep 02 2008 STATUS approved

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Last modified August 16 23:58 EDT 2018. Contains 313809 sequences. (Running on oeis4.)