7.6. 1.2+2.3+3.4+.........................upto n'th term.

#include<stdio.h> 
#include<conio.h>
void main ()
{
int i,n, sum=0;
clrscr ();
printf("How many number: ");
scanf("%d", &n);
for (i=1; i<=n, i++)
sum=sum+i*(i+1);
printf("Sum= %d", sum); 
getch(); 
}