A141111 Primes of the form 4*x^2+x*y-4*y^2 (as well as of the form 4*x^2+9*x*y+y^2).

29, 61, 79, 101, 131, 139, 179, 181, 191, 199, 211, 251, 269, 311, 389, 419, 439, 491, 521, 569, 571, 599, 601, 641, 659, 701, 719, 751, 809, 829, 859, 881, 911, 919, 971, 991, 1031, 1039, 1049, 1069, 1091, 1109, 1171, 1231, 1249, 1291, 1301, 1361, 1381, 1429, 1439, 1459, 1481, 1499, 1511, 1531

Offset

1,1

Comments

Both have discriminant = 65. 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.

References

Z. I. Borevich and I. R. Shafarevich, Number Theory. Academic Press, NY, 1966.

D. B. Zagier, Zetafunktionen und quadratische Körper, Springer, 1981.

Links

Juan Arias-de-Reyna, Table of n, a(n) for n = 1..10000

Peter Luschny, Binary Quadratic Forms

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

Example

a(3)=79 because we can write 79=4*5^2+5*3-4*3^2 (or 79=4*2^2+9*2*3+3^2).

Mathematica

Select[Prime[Range[250]], MatchQ[Mod[#, 65], Alternatives[1, 4, 9, 14, 16, 29, 36, 49, 51, 56, 61, 64]]&] (* Jean-François Alcover, Oct 28 2016 *)

Prog

(Sage) # uses[binaryQF]
# The function binaryQF is defined in the link 'Binary Quadratic Forms'.
Q = binaryQF([4, 1, -4])
print(Q.represented_positives(1531, 'prime')) # Peter Luschny, Oct 27 2016

Crossrefs

Cf. A141112, A243170.

Sequence in context: A042680 A286005 A132770 * A122114 A173032 A142047

Adjacent sequences: A141108 A141109 A141110 * A141112 A141113 A141114

Keyword

nonn

Author

Laura Caballero Fernandez, Lourdes Calvo Moguer, Maria Josefa Cano Marquez, Oscar Jesus Falcon Ganfornina and Sergio Garrido Morales (oscfalgan(AT)yahoo.es), Jun 04 2008, Jun 05 2008

Status

approved