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 A165681 Primes p such that 3*p*(p-1)+1 is not prime. 3
 13, 17, 19, 23, 37, 41, 47, 61, 71, 73, 79, 83, 97, 101, 103, 107, 113, 127, 131, 139, 149, 151, 163, 167, 179, 181, 191, 193, 199, 211, 223, 227, 229, 233, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 317, 331, 337, 349, 359, 367, 373, 379, 383, 397, 401 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 FORMULA A000040 \ A165682. a(n) ~ n log n. - Charles R Greathouse IV, Feb 23 2017 MATHEMATICA Select[Prime[Range[90]], !PrimeQ[3#(#-1)+1]&]  (* Harvey P. Dale, Mar 18 2011 *) PROG (PARI) is(n)=isprime(n) && !isprime(3*n*(n-1)+1) \\ Charles R Greathouse IV, Feb 23 2017 CROSSREFS Cf. A165682, A165683. Sequence in context: A286042 A168447 A191059 * A214033 A268593 A175873 Adjacent sequences:  A165678 A165679 A165680 * A165682 A165683 A165684 KEYWORD nonn,easy AUTHOR Vincenzo Librandi, Sep 24 2009 EXTENSIONS 2 and 3 removed by R. J. Mathar, Sep 26 2009 STATUS approved

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Last modified February 21 05:23 EST 2020. Contains 332086 sequences. (Running on oeis4.)