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A.5 Orthogonal Polynomials  321

          4. Prove that the vector Appell equation, namely
                                  C = jC j−1 ,  j > 0,

                                    j
             is satisfied by the column vector

                          	 
  −1   	      
 −1     	     
 −1
                            j         p +1            j +2
                    C j =                      φ j+1          φ j+2
                            0    φ j    1              2
                                        −1        T

                              j + n − 1
                         ···              φ j+n−1  ,  n ≥ 1.
                               n − 1
                                                 n
          5. If

                                          m
                                 m

                          f nm =   (−1) r     φ r φ n−r ,  n ≥ m,
                                          r
                                r=0
             prove that
                                  f     =(n − m)f n−1,m .
                                   nm
          A.5    Orthogonal Polynomials

          The following brief notes relate to the Laguerre, Hermite, and Legendre
          polynomials which appear in the text.


          Laguerre Polynomials L  (α) (x) and L n (x)
                                  n
          Definition.
                                         n      (−1) x
                                                    r r

                        L (α) (x)=(n + α)!                 ,
                                           r!(n − r)! (r + α)!
                         n
                                        r=0

                                          n         n  x r

                         L n (x)= L (0) (x)=  (−1) r      .
                                  n                 r  r!
                                          r=0
          Rodrigues formula.
                                   e x                 d
                           L n (x)=  D (e −x n   D =     .
                                           x );
                                      n
                                   n!                 dx
          Generating function relation.
                                               ∞

                           (1 − t) −1 −xt/(1−t)  =  L n (x)t ;
                                   e
                                                       n
                                              n=0
          Recurrence relations.
                (n +1)L n+1 (x) − (2n +1 − x)L n (x)=+nL n−1 (x)=0,

                                         xL (x)= n[L n (x) − L n−1 (x)];
                                            n
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