/* Program 8-4

   Function to calculate a triangular number */

void calc_tri_num (int n)
 {
  int i, tri_num = 0;

  for ( i = 1 ; i <= n ; ++i )
   tri_num += i;

  printf ("Triangular number %d is %d\n", n, tri_num);
 }

main ()
{
 calc_tri_num (10);
 calc_tri_num (20);
 calc_tri_num (50);
}


/* Program Output

Triangular number 10 is 55
Triangular number 20 is 210
Triangular number 50 is 1275

*/