Codewars Perimeter of squares in a rectangle

import java.math.BigInteger;
public class SumFct {
	public static BigInteger perimeter(BigInteger n) {
        BigInteger[] arr = new BigInteger[n.intValue() + 1];

        arr[0] = BigInteger.ONE;
        arr[1] = BigInteger.ONE;
        BigInteger temp = BigInteger.ONE.add(BigInteger.ONE);
        for (int i = 2; i <= n.intValue(); i++) {
            arr[i] = arr[i - 1].add(arr[i - 2]);
            temp = temp.add(arr[i]);
        }

        return temp.multiply(BigInteger.valueOf(4L));
    
	}
}