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A139856 Primes of the form 5x^2 + 24y^2. 2

%I #18 Sep 08 2022 08:45:34

%S 5,29,101,149,269,389,461,509,701,821,941,1061,1109,1181,1229,1301,

%T 1709,1901,1949,2069,2141,2309,2381,2549,2621,2741,2789,2861,2909,

%U 3221,3389,3461,3581,3701,3821,3989,4229,4349,4421,5021,5189,5261

%N Primes of the form 5x^2 + 24y^2.

%C Discriminant=-480. See A139827 for more information.

%C Except for 5, also primes of the form 21x^2+6xy+29y^2. See A140633. - _T. D. Noe_, May 19 2008

%H Vincenzo Librandi and Ray Chandler, <a href="/A139856/b139856.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 Except for 5, the primes are congruent to {29, 101} (mod 120).

%t QuadPrimes2[5, 0, 24, 10000] (* see A106856 *)

%o (Magma) [5] cat [ p: p in PrimesUpTo(6000) | p mod 120 in {29, 101}]; // _Vincenzo Librandi_, Jul 29 2012

%o (PARI) list(lim)=my(v=List(),w,t); for(x=1, sqrtint(lim\5), w=5*x^2; for(y=0, sqrtint((lim-w)\24), if(isprime(t=w+24*y^2), listput(v,t)))); Set(v) \\ _Charles R Greathouse IV_, Feb 22 2017

%Y Cf. A140633.

%K nonn,easy

%O 1,1

%A _T. D. Noe_, May 02 2008

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Last modified April 23 07:16 EDT 2024. Contains 371905 sequences. (Running on oeis4.)