Zeta2(s1,s2),Zeta3(s1,s2,s3):Integral Expressions and Approximates
  For the multiple zeta function zeta2(s1,s2) of two variables,we obtain its integral representation(involving product of Hurwitz zeta functions) over the interval [1,infinity),with respect to second variable of Hurwitz zeta function and also obtain a good approximate to it as a function of s1 and s2,for s1>=1 and s2>1.In particular this approximate is explicitly computable,when s1,s2 differ by an even integer and is good,when s2 is large.We treat zeta3(s1,s2,s3) likewise. 
V.V. Rane
math.NT