A243178 Numbers of the form x^2+xy+9y^2.

0, 1, 4, 9, 11, 15, 16, 21, 25, 29, 35, 36, 39, 44, 49, 51, 60, 64, 65, 71, 79, 81, 84, 85, 91, 99, 100, 109, 116, 119, 121, 135, 140, 141, 144, 149, 151, 156, 165, 169, 176, 179, 189, 191, 196, 204, 211, 219, 221, 225, 231, 235, 239, 240, 249, 256, 260, 261, 275, 281, 284, 289, 291, 309, 315, 316, 319, 324, 329, 331, 336, 340, 351, 359, 361, 364, 365, 375

Offset

1,3

Comments

Discriminant -35.

Links

Table of n, a(n) for n=1..78.

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

Mathematica

ofTheFormQ[n_] := Reduce[n == x^2 + x*y + 9*y^2, {x, y}, Integers] =!= False; Select[Range[0, 400], ofTheFormQ] (* Jean-François Alcover, Jun 04 2014 *)

Crossrefs

Primes: A106881.

Sequence in context: A050627 A036435 A162188 * A312834 A312835 A250176

Adjacent sequences: A243175 A243176 A243177 * A243179 A243180 A243181

Keyword

nonn

Author

N. J. A. Sloane, Jun 02 2014

Status

approved