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For the second integral,
                                                             The Coefficients of q(n)   25


                             1      Fàz) − φ(z)           1                1
                                                 dz             · 2exp           · 2πØ
                           2πi   B      z n+1           2πØ  n+1         1 − r

                                                       2          1
                                                          exp           .
                                                       r n      1 − r
                        And this is even smaller than our previous estimate. So combining
                        the two gives, by (15),

                                                  (1 − r) 5/2     π 2   1
                              p(n) − q(n)   M               exp               .      à 17)
                                                     r n           6 1 − r


                        But what is r? Answer: anything we please (as long as 0 <Ø <
                        1)! We are masters of the choice, and so we attempt to minimize
                        the right-hand side. The exact minimum is too complicated but the
                                                                  2
                                                        1
                        approximate one occurs when   n(r−1) exp  π  1   is minimized and
                                                      e          6 1−r
                                                                               π
                        this occurs when  π  2  1    n(1 − r), i.e., r   1 − √ .Sowe
                                           6 1−r                               6n
                        choose this r and, by so doing, we obtain, from (17), the bound

                                                                   √
                                       p(n)   q(n) + O n     −5/4 π  n/6  .          à 18)
                                                                e


                        The Coefficients of q(n)


                        The elementary function φ(z) has a rather pleasant definite integral
                        representation which will then lead to a handy expression for the
                        q(n).
                           If we simply begin with the well-known identity

                                                  ∞    2      √
                                                    e −t  dt    π
                                                 −∞
                        and make a linear change of variables (a > 0),

                                                                √

                                               ∞         2        π
                                                 e −(at−bð  dt      ,
                                                                 a
                                              −∞
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