A020686 Numbers of form 5 x^2 + 7 y^2.

0, 5, 7, 12, 20, 27, 28, 33, 45, 48, 52, 63, 68, 73, 80, 83, 87, 108, 112, 117, 125, 132, 143, 153, 157, 175, 180, 187, 188, 192, 195, 208, 220, 237, 243, 245, 252, 255, 257, 272, 273, 292, 297, 300, 308, 320, 327, 332, 343, 348, 355, 357, 363, 377, 383, 388, 405, 412, 420

Offset

1,2

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

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

Mathematica

Module[{upto=500, nn}, nn=Ceiling[Sqrt[upto/5]]; Select[Union[5#[[1]]^2+ 7#[[2]]^2 &/@ Tuples[Range[0, nn], 2]], #<=upto&]] (* Harvey P. Dale, Jan 20 2016 *)

Crossrefs

Sequence in context: A160243 A373669 A247027 * A011984 A280291 A195557

Adjacent sequences: A020683 A020684 A020685 * A020687 A020688 A020689

Keyword

easy,nonn

Author

David W. Wilson

Status

approved