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%I #10 Oct 25 2016 14:53:54
%S 7,11,19,23,43,67,79,83,103,107,191,199,227,251,263,283,359,367,379,
%T 383,419,431,467,479,503,523,563,571,619,631,643,659,727,743,751,787,
%U 827,839,907,911,919,971,983,1019,1031,1063,1091,1103,1123,1171,1187,1259
%N Primes of the form -2*x^2+6*x*y+7*y^2 (as well as of the form 14*x^2+22*x*y+7*y^2).
%C Discriminant = 92. Class = 2. Binary quadratic forms a*x^2+b*x*y+c*y^2 have discriminant d=b^2-4ac and gcd(a,b,c)=1.
%D Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966.
%D D. B. Zagier, Zetafunktionen und quadratische Körper, Springer, 1981.
%e a(5)=43 because we can write 43=-2*10^2+6*10*3+7*3^2 (or 14*1^2+22*1*1+7*1^2).
%t Reap[For[p = 2, p < 2000, p = NextPrime[p], If[FindInstance[p == -2*x^2 + 6*x*y + 7*y^2, {x, y}, Integers, 1] =!= {}, Print[p]; Sow[p]]]][[2, 1]] (* _Jean-François Alcover_, Oct 25 2016 *)
%Y Cf. A141336 (d=92).
%K nonn
%O 1,1
%A Laura Caballero Fernandez, Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (oscfalgan(AT)yahoo.es), Jun 25 2008
%E More terms from _Colin Barker_, Apr 05 2015
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