Table of 4-tuples (d,a,b,c) of quadratic forms having the number of discriminants d given in A107628.
-3, 1, 1, 1, -4, 1, 0, 1, -7, 1, 1, 2, -8, 1, 0, 2, -11, 1, 1, 3, -12, 1, 0, 3, -15, 1, 1, 4, -15, 2, 1, 2, -16, 1, 0, 4, -19, 1, 1, 5, -20, 1, 0, 5, -20, 2, 2, 3, -23, 1, 1, 6, -23, 2, 1, 3, -24, 1, 0, 6, -24, 2, 0, 3, -27, 1, 1, 7, -28, 1, 0, 7, -31, 1, 1, 8
1
This is sequence S000137 with the discriminant prepended.
T. D. Noe, Plot of 1000 4-tuples
T. D. Noe, Table of 1000 4-tuples
(Mma) dLim = 100; cnt = 0; dLst = {}; nn = Ceiling[dLim/4]; Do[d = b^2 - 4 a c; If[GCD[a, b, c] == 1 && 0 < -d < dLim, cnt++; AppendTo[dLst, {-d, a, b, c}]], {b, 0, nn}, {a, b, nn}, {c, a, nn}]; dLst = Sort[dLst]; tr = Transpose[dLst]; tr[[1]] = -tr[[1]]; Flatten[Transpose[tr]]
sign,tabl,nice
T. D. Noe, Jul 15 2014