A309137 Nonnegative integers of the form 5*x^2 + 5*x*y - y^2.

0, 5, 9, 11, 20, 29, 36, 41, 44, 45, 59, 71, 80, 81, 89, 95, 99, 101, 116, 125, 131, 144, 149, 155, 164, 171, 176, 179, 180, 191, 209, 225, 236, 239, 245, 251, 261, 269, 275, 279, 281, 284, 305, 311, 320, 324, 341, 356, 359, 369, 380, 389, 395, 396, 401, 404

Offset

1,2

Comments

Equivalent quadratic form: 9*x^2+15*x*y+5*y^2.

Discriminant of indefinite binary quadratic form: 45.

Nonnegative numbers of the form 5x^2 - 9y^2. - Jon E. Schoenfield, Jun 03 2022

Links

Table of n, a(n) for n=1..56.

Will Jagy, C++ program Conway_Positive_All.cc to find all positive numbers represented by an indefinite binary quadratic form

Peter Luschny, Binary Quadratic Forms

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

Prog

(C++) See Jagy link.

Crossrefs

Primes in this sequence: A141785.

Sequence in context: A102182 A100141 A314604 * A190894 A214262 A288143

Adjacent sequences: A309134 A309135 A309136 * A309138 A309139 A309140

Keyword

nonn

Author

Hugo Pfoertner, Jul 14 2019

Status

approved