OFFSET
1,3
COMMENTS
Discriminant 32.
Also numbers representable as x^2 + 6*x*y + y^2 with 0 <= x <= y. - Gheorghe Coserea, Jul 29 2018
Also numbers of the form x^2 - 8*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)
MATHEMATICA
Reap[For[n = 0, n <= 300, n++, If[Reduce[ x^2 + 4*x*y - 4*y^2 == n, {x, y}, Integers] =!= False, Sow[n]]]][[2, 1]]
PROG
(PARI)
seq(M, k=6) = {
setintersect([1..M], setbinop((x, y)->x^2 + k*x*y + y^2, [0..1+sqrtint(M)]));
};
concat(0, seq(292)) \\ Gheorghe Coserea, Jul 31 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, May 31 2014
STATUS
approved