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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def A_term(i,r,u,l1,l2,PAx,PBx,CPx,gamma):
 """ THO eq. 2.18 1.0 1.0 -1.0 1.0 -2.0 1.0 -0.5 0.5 """

    return pow(-1,i)*binomial_prefactor(i,l1,l2,PAx,PBx)*\
           pow(-1,u)*factorial(i)*pow(CPx,i-2*r-2*u)*\
           pow(0.25/gamma,r+u)/factorial(r)/factorial(u)/factorial(i-2*r-2*u)