A243174 Nonnegative integers of the form x^2 + 5*x*y - 5*y^2 (discriminant 45).

0, 1, 4, 9, 16, 19, 25, 31, 36, 45, 49, 55, 61, 64, 76, 79, 81, 99, 100, 109, 121, 124, 139, 144, 145, 151, 169, 171, 180, 181, 196, 199, 205, 211, 220, 225, 229, 241, 244, 256, 261, 271, 279, 289, 295, 304, 316, 319, 324, 331, 349, 355, 361, 369, 379, 396, 400, 405, 409, 421, 436, 439, 441, 445, 451, 475, 484, 495, 496, 499, 505, 529, 531, 541, 549

Offset: 1

Author

N. J. A. Sloane, Jun 01 2014

Keywords

• nonn

Comments

Also numbers representable as x^2 + 7*x*y + y^2 with 0 <= x <= y. - Gheorghe Coserea, Jul 29 2018

Also numbers of the form x^2 - x*y - 11*y^2 with 0 <= x <= y (or x^2 + x*y - 11*y^2 with x, y nonnegative). - Jianing Song, Jul 31 2018

Also nonnegative integers of the form 9x^2 - 5y^2. - Jon E. Schoenfield, Jun 03 2022

Links

• Gheorghe Coserea, Table of n, a(n) for n = 1..100001
• N. J. A. Sloane et al., Binary Quadratic Forms and OEIS (Index to related sequences, programs, references)

Crossrefs

Cf. A028957, A031363.

Primes: A033212.