[RESOLVED] calculating maximum distinct char permutations

if I have four characters: R, G, B, Y, I can calculate the maximum possible permutations as they are distinct characters and the maximum is 24, which is the factorial of 4.
but if the characters are: R, G, B, Y, R, the maximum is 60, but I can't work out a formula. also six characters R, G, B, Y, R, G, the maximum is 180...



there must be a simple formula for calculating those numbers. can anyone help with this?

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