12⁢πn⁢∫-π,πn∏1≤j<k≤nⅇⅈ⁢θj-ⅇⅈ⁢θk2⁢b⁢ⅆ⁡θ1⁢⋯⁢ⅆ⁡θn=Γ⁡1+b⁢nΓ⁡1+bn,