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%I #20 Sep 08 2022 08:45:18
%S 2,23,29,53,71,149,191,197,239,263,317,359,389,431,557,599,653,701,
%T 743,821,863,911,1031,1061,1103,1229,1367,1373,1439,1493,1583,1607,
%U 1709,1733,1871,1877,1901,1997,2039,2069,2087,2111,2207,2213,2237
%N Primes of the form 2x^2 + 21y^2.
%C Discriminant = -168. See A107132 for more information.
%H Vincenzo Librandi and Ray Chandler, <a href="/A107148/b107148.txt">Table of n, a(n) for n = 1..10000</a> [First 1000 terms from Vincenzo Librandi]
%H N. J. A. Sloane et al., <a href="https://oeis.org/wiki/Binary_Quadratic_Forms_and_OEIS">Binary Quadratic Forms and OEIS</a> (Index to related sequences, programs, references)
%F The primes are congruent to {2, 23, 29, 53, 71, 95, 149} (mod 168). - _T. D. Noe_, May 02 2008
%t QuadPrimes2[2, 0, 21, 10000] (* see A106856 *)
%o (Magma) [ p: p in PrimesUpTo(3000) | p mod 168 in {2, 23, 29, 53, 71, 95, 149} ]; // _Vincenzo Librandi_, Jul 24 2012
%o (PARI) list(lim)=my(v=List([2]), s=[23, 29, 53, 71, 95, 149]); forprime(p=23, lim, if(setsearch(s, p%168), listput(v, p))); Vec(v) \\ _Charles R Greathouse IV_, Feb 09 2017
%Y Cf. A139827.
%K nonn,easy
%O 1,1
%A _T. D. Noe_, May 13 2005
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