%I #15 Feb 18 2022 16:09:26
%S 19,59,89,101,149,151,179,191,229,239,251,271,281,331,349,359,389,409,
%T 421,461,491,509,569,599,631,659,661,701,739,761,769,829,859,919,971,
%U 1019,1021,1039,1069,1109,1171,1181,1249,1259,1279,1291,1301,1361,1381
%N Primes of the form x^2 + 9*x*y - y^2 (as well as of the form 9*x^2 + 11*x*y + y^2).
%C Discriminant = 85. Class = 2. Binary quadratic forms a*x^2 + b*x*y + c*y^2 have discriminant d = b^2 - 4ac.
%D Z. I. Borevich and I. R. Shafarevich, Number Theory.
%H N. J. A. Sloane et al., <a href="/wiki/Binary_Quadratic_Forms_and_OEIS">Binary Quadratic Forms and OEIS</a>: Index to related sequences, programs, references. OEIS wiki, June 2014.
%H D. B. Zagier, <a href="https://doi.org/10.1007/978-3-642-61829-1">Zetafunktionen und quadratische Körper</a>, Springer, 1981.
%e a(1) = 19 because we can write 19 = 1^2 + 9*1*3 - 3^2.
%Y Cf. A141772 (d=85).
%K nonn
%O 1,1
%A Laura Caballero Fernandez, Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (sergarmor(AT)yahoo.es), Jul 04 2008
%E More terms from _Colin Barker_, Apr 04 2015