OFFSET
1,2
COMMENTS
Discriminant 57.
Note that 3*x^2+3*x*y-4*y^2=n is equivalent to 3*z^2 - 19*y^2=4*n where z=2*x+y. - Robert Israel, Jun 10 2014
LINKS
Robert Israel, Table of n, a(n) for n = 1..3000
N. J. A. Sloane et al., Binary Quadratic Forms and OEIS (Index to related sequences, programs, references)
MAPLE
select(m -> nops([isolve(3*z^2-19*y^2=4*m)])>0, [$0..1000]); # Robert Israel, Jun 10 2014
MATHEMATICA
Reap[For[n = 0, n <= 30, n++, If[Reduce[3*x^2 + 3*x*y - 4*y^2 == n, {x, y}, Integers] =!= False, Sow[n]]]][[2, 1]]
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 06 2014
EXTENSIONS
More terms from Colin Barker, Jun 10 2014
STATUS
approved