A242666 Nonnegative integers of the form -x^2 + 4xy + 3y^2.

0, 3, 6, 7, 12, 14, 19, 24, 27, 28, 31, 38, 47, 48, 54, 56, 59, 62, 63, 75, 76, 83, 87, 94, 96, 103, 108, 111, 112, 118, 124, 126, 131, 139, 147, 150, 152, 159, 166, 167, 171, 174, 175, 188, 192, 199, 203, 206, 216, 222, 223, 224, 227, 236, 243, 248, 251, 252, 259, 262, 271, 278, 279, 283, 294, 300

Offset: 1

Author

N. J. A. Sloane, May 31 2014

Keywords

• nonn

Comments

Discriminant 28.

Nonnegative numbers of the form 7x^2 - y^2. - Jon E. Schoenfield, Jun 03 2022

For the subsequence of the numbers with proper representations (gcd(x, y) = 1) see A359476. ~ Wolfdieter Lang, Jan 17 2023

Links

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

Crossrefs

Primes in this sequence = A141173.

Cf. A242662, A359476.

Programs

Mathematica

Reap[For[n = 0, n <= 300, n++, If[Reduce[-x^2 + 4*x*y + 3*y^2 == n, {x, y}, Integers] =!= False, Sow[n]]]][[2, 1]]