A106753 - OEIS

%I #3 Oct 12 2012 14:39:32

%S 3,7,8,11,12,15,19,20,23,24,27,28,31,32,35,39,40,43,44,47,48,51,52,55,

%T 56,59,60,63,67,68,71,72,75,76,79,80,83,84,87,88,91,92,95,96,99,103,

%U 104,107,108,111,112,115,116,119,120,123,124,127,128,131,132,135,136,139

%N Discriminants, negated, of definite binary quadratic forms.

%C A definite binary quadratic form a*x^2 + b*x*y + c*y^2 over the integers has discriminant D = b^2 - 4*a*c < 0; -D is assumed to be a nonsquare.

%F -a(n) is 0 (mod 4) or 1 (mod 4), but not a square.

%t Select[ Range[148], (Mod[ -#, 4] == 0 || Mod[ -#, 4] == 1) && !IntegerQ[Sqrt[ # ]] & ]

%Y Cf. A014601, A042948 (with squares), A079896 (indefinite case).

%K easy,nonn

%O 1,1

%A _Steven Finch_, May 16 2005