Sylvester versus Gundelfinger

Abstract

Let Vn be the SL₂-module of binary forms of degree n and let V=V₁⊕V₃⊕V₄. We show that the minimum number of generators of the algebra R=C[V]SL₂ of polynomial functions on V invariant under the action of SL₂ equals 63. This settles a 143-year old question.