Classification of Normal Subgroups of Hecke Group H6 in Terms of Parabolic Class Number
Classification of Normal Subgroups of Hecke Group H6 in Terms of Parabolic Class Number
In [3], Greenberg showed that n≤6t3 so that μ = nt≤6t4 for a normal subgroup N of level n and index μ having t parabolic classes in the modular group Γ. Accola, [1], improved these to n≤6t2 always and n≤t2 if Γ/N is not abelian. Newman, [5], obtained another generalisation …