The second of these relations enables the calculation of the 3rd virial coefficient C(T). (Let me leave the calculation of J3 and C(T), for the hardball model, for the reader's exe...The second of these relations enables the calculation of the 3rd virial coefficient C(T). (Let me leave the calculation of J3 and C(T), for the hardball model, for the reader's exercise.) Evidently, a more complete solution of Eqs. (???), (???), and (???) may be used to calculate an arbitrary virial coefficient, though starting from the 5th coefficient, such calculations may be completed only numerically even in the simplest hardball model.