A020671 Numbers of form x^2 + 8 y^2.

0, 1, 4, 8, 9, 12, 16, 17, 24, 25, 32, 33, 36, 41, 44, 48, 49, 57, 64, 68, 72, 73, 76, 81, 88, 89, 96, 97, 100, 108, 113, 121, 128, 129, 132, 136, 137, 144, 152, 153, 164, 169, 172, 176, 177, 192, 193, 196, 200, 201, 204, 209, 216, 225, 228, 233, 236, 241, 249, 256, 257

Offset: 1

Author

David W. Wilson

Keywords

• easy
• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..10000
• N. J. A. Sloane et al., Binary Quadratic Forms and OEIS (Index to related sequences, programs, references)

Crossrefs

Cf. A007519.

Programs

Magma

[n: n in [0..230] | NormEquation(8, n) eq true]; // Vincenzo Librandi, Aug 31 2016

Mathematica

lim=260; k=8; Union@Flatten@Table[x^2 + k y^2, {y, 0, Sqrt[lim/k]}, {x, 0, Sqrt[lim-k y^2]}] (* Vincenzo Librandi, Aug 31 2016 *)