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Numbers k such that k^2 + k + 7 is prime.
3

%I #30 Aug 11 2024 14:41:29

%S 0,2,3,5,8,9,11,12,17,18,24,26,29,30,32,33,38,39,44,50,51,57,59,65,71,

%T 74,86,89,92,95,96,99,102,108,113,122,123,128,131,134,135,137,141,143,

%U 144,156,159,164,165,170,173,176,177,180,183,198,201,206

%N Numbers k such that k^2 + k + 7 is prime.

%H Harvey P. Dale, <a href="/A027756/b027756.txt">Table of n, a(n) for n = 1..1000</a>

%H P. De Geest, <a href="https://www.worldofnumbers.com/index.html">World!Of Numbers</a>

%t Select[Range[0,250],PrimeQ[#^2+#+7]&] (* _Harvey P. Dale_, Oct 10 2011 *)

%o (Magma) [n: n in [0..250] | IsPrime(n^2+n+7)]; // _Vincenzo Librandi_, Nov 20 2010

%o (PARI) is(n)=isprime(n^2+n+7) \\ _Charles R Greathouse IV_, Feb 20 2017

%Y Cf. A005471 (associated primes).

%K nonn,easy

%O 1,2

%A _Patrick De Geest_