A034021 Numbers that are primitively but not imprimitively represented by x^2+xy+y^2.

0, 1, 3, 7, 13, 19, 21, 31, 37, 39, 43, 57, 61, 67, 73, 79, 91, 93, 97, 103, 109, 111, 127, 129, 133, 139, 151, 157, 163, 181, 183, 193, 199, 201, 211, 217, 219, 223, 229, 237, 241, 247, 259, 271, 273, 277, 283, 291, 301, 307, 309, 313, 327, 331, 337, 349, 367

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Comments

Also numbers that are squarefree and primitively represented by x^2+x*y+y^2. - Frank M Jackson, Nov 08 2013

Crossrefs

Cf. A034017, A003136, A045897.

Programs

Mathematica

lst = {}; Do[k=x^2+x*y+y^2; If[(SquareFreeQ[k] && GCD[x, y]==1) || k==0, AppendTo[lst, k]], {x, 0, 100}, {y, 0, x}]; Union@lst (* Frank M Jackson, Nov 08 2013 *)

Extensions

Extended by Ray Chandler, Jan 29 2009