++tye for generating the excellent formula. Lots of interesting math involved in seemingly simple looking problem. Why the formula make sense is a very good question and I don't have answer at the moment.

I had suspected the factorials once I saw symmetry and little similarity with pascal's triangle, but tye came out faster even with the solution.

artist

In reply to Re: Re^2: Parens permutations (formula) by artist
in thread Parens permutations by artist

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