A243704 Primes represented by the indefinite quadratic form -x^2+13xy+9y^2.

31, 41, 61, 251, 349, 379, 389, 401, 419, 431, 449, 461, 491, 619, 631, 739, 769, 811, 821, 829, 1009, 1061, 1171, 1181, 1229, 1231, 1279, 1289, 1321, 1361, 1451, 1471, 1499, 1601, 1699, 1721, 1759, 1861, 2081, 2131, 2239, 2339, 2341, 2411, 2551, 2579, 2591, 2789

Offset: 1

Author

N. J. A. Sloane, Jun 17 2014

Keywords

• nonn

Comments

Discriminant 205.

4*a(n) has the form 205*y^2 - z^2, where z = 2*x-13*y. [Bruno Berselli, Jun 20 2014]

Links

• N. J. A. Sloane et al., Binary Quadratic Forms and OEIS (Index to related sequences, programs, references)

Crossrefs

Primes in A243703.

Programs

PARI

fc(a,b,c,M) = {
my(t1=List(),t2);
forprime(p=2,prime(M),
t2 = qfbsolve(Qfb(a,b,c),p);
if(t2 != 0, listput(t1,p))
);
Vec(t1)
};
fc(-1,13,9,600)