Sum of perimeter of all the squares in a rectangle using JavaScript

Problem Suppose there are 5 squares embedded inside a rectangle like this −

Their perimeter will be −

4 + 4 + 8 + 12 + 20 = 48 units

We are required to write a JavaScript function that takes in a number n and return the sum of the perimeter if there are n squares embedded.

Example

Following is the code −

const num = 6;
const findPerimeter = (num = 1) => {
   const arr = [1,1];
   let n = 0;
   let sum = 2;
   for(let i = 0 ; i < num-1 ; i++){
      n = arr[i] + arr[i+1];
      arr.push(n);
      sum += n;
   };
   return sum * 4;
};
console.log(findPerimeter(num - 1));

Output

80