A034019 Numbers that are imprimitively (and possibly also primitively) represented by x^2+xy+y^2.

4, 9, 12, 16, 25, 27, 28, 36, 48, 49, 52, 63, 64, 75, 76, 81, 84, 100, 108, 112, 117, 121, 124, 144, 147, 148, 156, 169, 171, 172, 175, 189, 192, 196, 208, 225, 228, 243, 244, 252, 256, 268, 279, 289, 292, 300, 304, 316, 324, 325, 333, 336, 343

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A045897, A034018, A003136.

Programs

PARI

is(n)=my(f=factor(n),t); for(i=1, #f[, 1], if(f[i, 1]%3<2 && f[i,2]>1, t=1); if(f[i,1]%3==2, if(f[i,2]%2, return(0), t=1))); t \\ Charles R Greathouse IV, Nov 04 2015