%I #16 Jan 17 2023 03:32:49

%S 0,3,6,7,12,14,19,24,27,28,31,38,47,48,54,56,59,62,63,75,76,83,87,94,

%T 96,103,108,111,112,118,124,126,131,139,147,150,152,159,166,167,171,

%U 174,175,188,192,199,203,206,216,222,223,224,227,236,243,248,251,252,259,262,271,278,279,283,294,300

%N Nonnegative integers of the form -x^2 + 4xy + 3y^2.

%C Discriminant 28.

%C Nonnegative numbers of the form 7x^2 - y^2. - _Jon E. Schoenfield_, Jun 03 2022

%C For the subsequence of the numbers with proper representations (gcd(x, y) = 1) see A359476. ~ _Wolfdieter Lang_, Jan 17 2023

%H N. J. A. Sloane et al., <a href="https://oeis.org/wiki/Binary_Quadratic_Forms_and_OEIS">Binary Quadratic Forms and OEIS</a> (Index to related sequences, programs, references)

%t Reap[For[n = 0, n <= 300, n++, If[Reduce[-x^2 + 4*x*y + 3*y^2 == n, {x, y}, Integers] =!= False, Sow[n]]]][[2, 1]]

%Y Primes in this sequence = A141173.

%Y Cf. A242662, A359476.

%K nonn

%O 1,2

%A _N. J. A. Sloane_, May 31 2014