A028954 Numbers represented by quadratic form with Gram matrix [ 2, 1; 1, 6 ]. (divided by 2).

0, 1, 3, 4, 5, 9, 11, 12, 15, 16, 20, 23, 25, 27, 31, 33, 36, 37, 44, 45, 47, 48, 49, 53, 55, 59, 60, 64, 67, 69, 71, 75, 80, 81, 89, 92, 93, 97, 99, 100, 103, 108, 111, 113, 115, 121, 124, 125, 132, 135, 137, 141, 144, 147, 148, 155, 157, 159, 163, 165, 169, 176, 177

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Comments

Numbers represented by the form x^2+xy+3y^2 of discriminant -11.

Links

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

Crossrefs

Cf. A028927. For primes see A056874.

Programs

Mathematica

Reap[For[n = 0, n < 200, n++, r = Reduce[x^2 + x y + 3 y^2 == n, {x, y}, Integers]; If[r =!= False, Sow[n]]]][[2, 1]] (* Jean-François Alcover, Oct 31 2016 *)

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), Mar 29 2000