A097700 Numbers not of form x^2 + 2y^2.

5, 7, 10, 13, 14, 15, 20, 21, 23, 26, 28, 29, 30, 31, 35, 37, 39, 40, 42, 45, 46, 47, 52, 53, 55, 56, 58, 60, 61, 62, 63, 65, 69, 70, 71, 74, 77, 78, 79, 80, 84, 85, 87, 90, 91, 92, 93, 94, 95, 101, 103, 104, 105, 106, 109, 110, 111, 112, 115, 116, 117, 119, 120, 122

Offset: 1

Author

Ralf Stephan, Aug 23 2004

Keywords

• nonn

Comments

Is lim_{n->inf} a(n)/n = 3/4?

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..6800

Crossrefs

Complement of A002479.

Programs

Magma

[n: n in [0..160] | NormEquation(2, n) eq false]; // Vincenzo Librandi, Jan 15 2017

Mathematica

formQ[n_]:=Reduce[x>=0&&y>=0&&n==x^2 + 2 y^2, {x, y}, Integers]==False; Select[Range[0, 200], formQ] (* Vincenzo Librandi, Jan 15 2017 *)