1,3

For number of monomials in discriminant of symbolic polynomial n degree with all non-zero coefficients see A007878

For number of monomials in discriminant of symbolic polynomial n degree with only one zero coefficient by x^(n-1) see A138800

For number of monomials in discriminant of symbolic Tschirnhausen (with three zeros coefficients by x^(n-1) and x^(n-2) and x^(n-3)) polynomial n degree see A138802

a(5)=6 because discriminant of quintic x^5+a*x^2+b*x+c is equal: -27a^4 b^2 + 256b^5 + 108a^5 c - 1600a b^3 c + 2250a^2 b c^2 + 3125 c^4 consist of 6 monomials (parts)

ClearAll[f]; a = {1, 1}; Do[k = 0; Do[If[n > s, If[(n > s - 1) && ((n > s - 2)), k = k + f[n] x^n], k = k + x^n], {n, 0, s}]; m = Resultant[k, D[k, x], x]; AppendTo[a, Length[m]], {s, 3, 9}]; a (*Artur Jasinski*)

Cf. A007878, A138787, A138788, A138800, A138802.

Sequence in context: A097090 A085403 A112478 this_sequence A069466 A141902 A143084

Adjacent sequences: A138798 A138799 A138800 this_sequence A138802 A138803 A138804

nonn

Artur Jasinski (grafix(AT)csl.pl), Mar 30 2008