Fuchsian differential equations Hj of order j = 3, ..., 6 with three singular points and one accessory parameter are presented. The shift operators for H6 are studied. They lead to assign the accessory parameter of H6 a cubic polynomial of local exponents so that the equation has several nice symmetries. The other equations will be studied in the forthcoming papers.
Haraoka et al. (Wed,) studied this question.