Display Numbers from 1 to n and their Sum

/*
Write a program to display numbers from 1 to n and their sum.
*/
#include<stdio.h>
int summation(int n);
void display1(int n);
void display2(int n);

main()
{
 int n;
 printf("Enter number of terms : ");
 scanf("%d", &n);
 display1(n);
 printf("\n");
 display2(n);
 printf("\n");
 printf("sum = %d\n", summation(n));
}

/*summation*/

int summation( int n)

{
 if(n==0)
 return 0;
 return ( n + summation(n-1) );
}

/*display1*/
void display1(int n)

{
 if( n==0 )
 return;
 printf("%d ",n);
 display1(n-1);
}

/*display2*/

void display2(int n){
 if( n==0 )
 return;
 display2(n-1);
 printf("%d ",n);
}