(1.2)+(3.4)+(5.6)+............n

 

1.2+3.4+5.6+............n

 

//1.2+3.4+5.6+............n

#include<stdio.h>

int main()

{

    int n,i,sum=0;

    printf("enter number= ");

    scanf("%d",&n);

    for(i=2;i<=n;i=i+2)

         sum=sum+(i-1)*i;

    {

    printf("\n%d\n",sum);

    }

}