EN
Let p be a prime greater than 3. Consider the modular curve X₀(3p) over ℚ and its Jacobian variety J₀(3p) over ℚ. Let 𝓣(3p) and 𝓒(3p) be the group of rational torsion points on J₀(3p) and the cuspidal group of J₀(3p), respectively. We prove that the 3-primary subgroups of 𝓣(3p) and 𝓒(3p) coincide unless p ≡ 1 (mod 9) and $3^{(p-1)/3} ≡ 1 (mod p)$.