A020677 Numbers of form 3*x^2 + 4*y^2.

0, 3, 4, 7, 12, 16, 19, 27, 28, 31, 36, 39, 43, 48, 52, 63, 64, 67, 75, 76, 79, 84, 91, 100, 103, 108, 111, 112, 124, 127, 139, 144, 147, 148, 151, 156, 163, 171, 172, 175, 183, 192, 196, 199, 208, 211, 219, 223, 228, 243, 244, 247, 252, 256, 259, 268, 271, 279, 283, 291

Offset

1,2

Comments

Each of these numbers is congruent to 0, 3, 4 or 7 mod 12. Therefore, except for 3, all the primes in this sequence are of the form 12k + 7. - Alonso del Arte, Jan 23 2014

Links

Table of n, a(n) for n=1..60.

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

Mathematica

max = 300; Select[Union[Flatten[Table[3x^2 + 4y^2, {x, 0, Ceiling[Sqrt[max/3]]}, {y, 0, Ceiling[Sqrt[max/4]]}]]], # < max &] (* Alonso del Arte, Jan 23 2014 *)

Crossrefs

Cf. A068229.

Sequence in context: A280991 A256726 A130324 * A362222 A310007 A158237

Adjacent sequences: A020674 A020675 A020676 * A020678 A020679 A020680

Keyword

easy,nonn

Author

David W. Wilson

Status

approved