A000394 Numbers of form x^2 + y^2 + 7z^2.

0, 1, 2, 4, 5, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 20, 23, 24, 25, 26, 27, 28, 29, 30, 32, 33, 34, 36, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 48, 49, 50, 52, 53, 54, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 67, 68, 69, 71, 72

Offset

0,3

Links

Table of n, a(n) for n=0..59.

Mathematica

r[n_] := Reduce[n == x^2 + y^2 + 7z^2, {x, y, z}, Integers]; Reap[For[n = 0, n <= 100, n++, If[r[n] =!= False, Print[n]; Sow[n]]]][[2, 1]] (* Jean-François Alcover, Feb 08 2016 *)

Crossrefs

Complement of A097633.

Sequence in context: A178344 A274333 A039241 * A039184 A039137 A071807

Adjacent sequences: A000391 A000392 A000393 * A000395 A000396 A000397

Keyword

nonn

Author

N. J. A. Sloane

Status

approved