#include <stdio.h> 

/* no prototype needed, but add them here if desired */ 
int Triangular_Number (int); 

//*********************************************************************
// 
// Function: Triangular_Number 
// 
// Description: A triangular number can be generated by the 
// the following formula: 
// 
// Triangular number = n (n + 1) / 2 
// 
// This function will return the triangular number 
// calculated based it being passed an integer value 
// 
// Parameters: theNumber - An integer value to start the 
// calculation of the Triangular Number. 
// 
// Returns: The Triangular Number that is calculated 
// 
//*********************************************************************

int Triangular_Number (int theNumber) 
{ 

    int tri_num; /* triangular number to be calculated */ 

    /* Calculate the Triangular Number */ 
    tri_num = (theNumber * (theNumber + 1))/2; 

    /* return to the calling function */ 
    return(tri_num); 

} /* end Triangular_Number */ 


int main (void) 
{ 

    int n;       /* a number to calculate a triangular number */ 
    int tri_num; /* The triangular number calculated from n */

    printf ("TABLE OF TRIANGULAR NUMBERS from 5 to 50 by 5\n\n"); 
    printf (" n  Triangular Number\n"); 
    printf ("--- -----------------\n"); 

    tri_num = 0; 

    /* Calculate and print triangular numbers from 5 to 50 in steps of 5 */ 
    for (n = 5; n <= 50; n += 5) 
    { 
     
        printf (" %-5i %-5i\n", n, Triangular_Number(n)); 
    } 

    return (0); /* indicate successful completion */ 

} /* end main */