359.LOLLIPOP, Bookended
★★★combinatoricsCh. 1 — Classical Probability and Combinatorics444+ Problems in Probability
How many distinguishable permutations of are there that start and end with the same letter? (E.g. is valid, as it starts and ends with L.)
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Only letters with at least two copies can bookend. Case on which letter it is and permute the remaining multiset.
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