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%I #18 Sep 08 2022 08:45:33
%S 5,41,89,101,269,461,509,521,761,881,929,941,1049,1109,1181,1301,1361,
%T 1601,1721,1889,1949,2141,2309,2441,2609,2621,2729,2789,2861,3041,
%U 3209,3449,3461,3701,3821,3881,3989,4049,4241,4289,4409,4721,4889
%N Primes of the form 5x^2 + 21y^2.
%C Discriminant = -420. See A139827 for more information.
%H Vincenzo Librandi and Ray Chandler, <a href="/A139846/b139846.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 {5, 41, 89, 101, 209, 269, 341} (mod 420).
%t QuadPrimes2[5, 0, 21, 10000] (* see A106856 *)
%o (Magma) [ p: p in PrimesUpTo(6000) | p mod 420 in {5, 41, 89, 101, 209, 269, 341}]; // _Vincenzo Librandi_, Jul 29 2012
%o (PARI) list(lim)=my(v=List([5]), s=[41, 89, 101, 209, 269, 341]); forprime(p=41, lim, if(setsearch(s, p%420), listput(v, p))); Vec(v) \\ _Charles R Greathouse IV_, Feb 10 2017
%K nonn,easy
%O 1,1
%A _T. D. Noe_, May 02 2008
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