#include <stdio.h>
main ()
{
 
   int n;         /* a number */
   int tri_num;   /* the triangular value of the number */
 
   printf ("TABLE OF TRIANGULAR NUMBERS by 5\n\n");
   printf (" n     Triangular Number\n");
   printf ("---    -----------------\n");
 
   tri_num = 0;
 
   n = 5;
   do
   {
       tri_num = (n * (n + 1))/2;
       printf (" %d        %d\n", n, tri_num);
       n = n + 5;  /* better:  n += 5; */
   }
   while (n <= 50);
   return (0);
}
 
/* with a while loop */

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