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A243179
Numbers of the form 3x^2+xy+3y^2.
1
0, 3, 5, 7, 12, 13, 17, 20, 27, 28, 33, 45, 47, 48, 52, 55, 63, 68, 73, 75, 77, 80, 83, 87, 97, 103, 105, 108, 112, 117, 125, 132, 143, 145, 147, 153, 157, 167, 173, 175, 180, 187, 188, 192, 195, 203, 208, 213, 220, 223, 227, 237, 243, 245, 252, 255, 257, 272, 273, 283, 292, 293, 297, 300, 307, 308, 313, 320, 325, 327, 332, 343, 348, 353, 355, 357, 363, 367
OFFSET
1,2
COMMENTS
Discriminant -35.
LINKS
N. J. A. Sloane et al., Binary Quadratic Forms and OEIS (Index to related sequences, programs, references)
MATHEMATICA
ofTheFormQ[n_] := Reduce[n == 3*x^2 + x*y + 3*y^2, {x, y}, Integers] =!= False; Select[Range[0, 400], ofTheFormQ] (* Jean-François Alcover, Jun 04 2014 *)
CROSSREFS
Primes: A106878.
Sequence in context: A121976 A339789 A293598 * A207459 A368036 A241515
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 02 2014
STATUS
approved