A106950 - OEIS

%I #33 Jul 22 2024 00:49:42

%S 19,43,67,73,97,139,163,193,211,241,283,307,313,331,337,379,409,433,

%T 457,499,523,547,571,577,601,619,643,673,691,739,769,787,811,859,883,

%U 907,937,1009,1033,1051,1123,1129,1153,1171,1201,1249,1291,1297,1321

%N Primes of the form x^2 + 18y^2.

%C Discriminant = -72.

%H Vincenzo Librandi and Ray Chandler, <a href="/A106950/b106950.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 Primes congruent to 1,19 modulo 24. - _Michael Somos_, Aug 19 2006

%t QuadPrimes2[1, 0, 18, 10000] (* see A106856 *)

%o (PARI) {a(n)= my(m, c); if(n<1, 0, c=0; m=0; while( c<n, m++; if( isprime(m)& m%24==1||m%24==19, c++)); m)} /* _Michael Somos_, Aug 19 2006 */

%o (Magma) [ p: p in PrimesUpTo(2000) | p mod 24 in {1, 19} ]; // _Vincenzo Librandi_, Jul 22 2012

%K nonn,easy

%O 1,1

%A _T. D. Noe_, May 09 2005