n^(n falling) / k1! k2! k3!
where n^(n falling) = n!
But if you have n items and want to paint k1 red and k2 blue, you can have
n^((k1 + k2) falling) / k1! k2!
without needing to explicitly write down the k3 = n - k1 - k2 items that are left unpainted.
n^(n falling) / k1! k2! k3!
where n^(n falling) = n!
But if you have n items and want to paint k1 red and k2 blue, you can have
n^((k1 + k2) falling) / k1! k2!
without needing to explicitly write down the k3 = n - k1 - k2 items that are left unpainted.
n^(|k| falling) / k1! k2! … km!
where |k| = k1 + … + km.
And this is even better! Because it works not only when |k| = n, when n^(n falling) = n!, but also when |k| < n, so you don't even have to write down the left-over number!
n^(|k| falling) / k1! k2! … km!
where |k| = k1 + … + km.
And this is even better! Because it works not only when |k| = n, when n^(n falling) = n!, but also when |k| < n, so you don't even have to write down the left-over number!