Computes the expected number of sections of degree a, in the ideal sheaf of a curve with genus g and degree d in P1*P1*P1.
i1 : expHilbFuncIdealSheaf(6,{5,5,5},{2,2,2}) o1 = 2
i2 : expHilbFuncIdealSheaf(9,{5,5,5},{2,2,1}) o2 = 1