|\^/|      MAPLE V
._|\|   |/|_.  Copyright (c) 1981-1990 by the University of Waterloo.
 \  MAPLE  /   All rights reserved.  MAPLE is a registered trademark of
 <____ ____>   Waterloo Maple Software.
      |        Type ? for help.

> x:=4; i:=5;
                                     x := 4
                                     i := 5
> x^i;

                                      1024
> sum(i^2,i=1..n);
Error, (in sum) summation variable previously assigned, 
                second argument evaluates to, 5 = 1 .. n
> i;

                                       5
> sum('i^2','i'=1..n);

                              3              2
                   1/3 (n + 1)  - 1/2 (n + 1)  + 1/6 n + 1/6
> i := 'i';

                                     i := i
> sum(i^2,i=1..n);

                              3              2
                   1/3 (n + 1)  - 1/2 (n + 1)  + 1/6 n + 1/6
> quit