# include <stdio.h>

//
//  Program 8.4, Stephen Kochan, Programming in C.
//

int main ( void );
void calculateTriangularNumber ( int n );


int main ( void )
{

  calculateTriangularNumber ( 10 );
  calculateTriangularNumber ( 20 );
  calculateTriangularNumber ( 50 );

  return 0;
}

void calculateTriangularNumber ( int n )
{
  int i, triangularNumber = 0;

  for ( i = 1; i <= n; i++ )
  {
    triangularNumber = triangularNumber + i;
  }

  printf ( "Triangular number %i is %i\n", n, triangularNumber );

  return;
}