Function            summation - calculate a summation of integers

  Syntax              int summation(int max);

  Prototype in        mathhk.h

  Remarks             summation calculates a summation denoted by . Xi
                      where i ranges from 1 to max. Beware of overflow,
                      calculations are done as ints.

  Return value        returns the summation denoted by . Xi where i
                      ranges from 1 to max. If max <= 1, summation
                      returns a 1.

  See also            average(), factorial(), stddev(), variance()

  Example             #include <mathhk.h>

                      main()
                      {
                           printf("Summation is %d\n",summation(10));
                      }

  Program output      Summation is 55