A243188 Nonnegative numbers of the form x^2 + 6*x*y - 6*y^2.

0, 1, 4, 9, 10, 16, 21, 25, 34, 36, 40, 49, 61, 64, 66, 81, 84, 85, 90, 100, 106, 109, 121, 129, 136, 144, 154, 160, 165, 169, 181, 189, 196, 201, 210, 225, 226, 229, 241, 244, 250, 256, 264, 265, 274, 289, 301, 306, 309, 324, 336, 340, 346, 349, 354, 360

Offset: 1

Author

N. J. A. Sloane, Jun 05 2014

Keywords

• nonn

Comments

Discriminant 60.

Also numbers representable as x^2 + 8*x*y + y^2 with 0 <= x <= y. - Gheorghe Coserea, Jul 29 2018

Also numbers of the form x^2 - 15*y^2. - Jianing Song, Jul 31 2018

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. A031363.

Primes: A107152.

Programs

Mathematica

Reap[For[n = 0, n <= 200, n++, If[Reduce[ 1*x^2 + 6*x*y - 6*y^2 == n, {x, y}, Integers] =!= False, Sow[n]]]][[2, 1]]

Extensions

More terms from Colin Barker, Apr 07 2015