C :

#include<stdio.h>
int f(int n){
	if(n==1){
		return 2;
	}else{
		return f(n-1) + 2*(n-1);
	}
}
void main(){
	int n;
	scanf("%d",&n);
	printf("%d",f(n));
}

C++ :

#include<iostream>
using namespace std;
int main()
{
   //A(n) = A(n-1) + 2(n-1)
   long long i,n,x;
   cin>>n;
   x = 2;
   if(n == 1){
   	  x = 2;
   }else{
   	  for(i = 2;i <= n;i++){
         x = x + 2 * (i - 1);   	  	
 	  } 
   }
   cout<<x<<endl;
   return 0;
}

Python :

n=int(input())
a=[0 for i in range(n+1)]
for i in range(1,n+1):
    if(i==1):
        a[1]=2
    else:
        a[i]=a[i-1]+2*(i-1)
print(a[n])