Fibonacci Modified

• Time : O(n)
• Space : O(1)

public static BigInteger fibonacciModified(int t1, int t2, int n) {
    if(n == 1) return BigInteger.valueOf(t1);
    if(n == 2) return BigInteger.valueOf(t1);
    BigInteger b1 = BigInteger.valueOf(t1), b2 = BigInteger.valueOf(t2);
    for(int i = 3; i <= n; i++) {
        BigInteger next = b1.add(b2.pow(2));
        b1 = b2;
        b2 = next;
    }
    return b2;
}