Human Calculators

Alice and Bob are siblings who are very good at calculating things. Both of them have set world records and are known as 'the human calculators'. Bob is faster at calculating things but Alice is better at mathematics. One day Bob challenged Alice to calculate f(n), where f(n) = 1n × 2n-1 × 3n-2 × ... × (n-1)2 × n Alice knew that Bob's math is weak, so she said, "This is too easy for me. I will