 The cusps are then given by the zero-level-sets of the representatives of the "A"2"n" equivalence classes, where "n" ≥ 1 is an integer.For a type "A"4-singularity we need "f" to have a degenerate quadratic part (this gives type "A"≥2), that "L" "does" divide the cubic terms (this gives type "A"≥3), another divisibility condition (giving type "A"≥4), and a final non-divisibility condition (giving type exactly "A"4).To see where these extra divisibility conditions come from, assume that "f" has a degenerate quadratic part "L"2 and that "L" divides the cubic terms.