Negative of discriminants of quadratic forms in S000137.
3, 4, 7, 8, 11, 12, 15, 15, 16, 19, 20, 20, 23, 23, 24, 24, 27, 28, 31, 31, 32, 32, 35, 35, 36, 36, 39, 39, 39, 40, 40, 43, 44, 44, 47, 47, 47, 48, 48, 51, 51, 52, 52, 55, 55, 55, 56, 56, 56, 59, 59, 60, 60, 63, 63, 63, 64, 64, 67, 68, 68, 68, 71, 71, 71, 71, 72
1
The number of terms having a given value can be found in A107628.
T. D. Noe, Plot of 1000 terms
T. D. Noe, Table of 1000 terms
(Mma) dLim = 500; 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]], {b, 0, nn}, {a, b, nn}, {c, a, nn}]; Sort[dLst]
Cf. S000137.
nonn
T. D. Noe, Jul 15 2014