Number of circular permutations of 2n letters that are free of jealousy.

A089039

Number of circular permutations of 2n letters that are free of jealousy.

Terms

    a(0) =1a(1) =2a(2) =6a(3) =60a(4) =960a(5) =24000a(6) =861840a(7) =42104160a(8) =2686763520a(9) =217039253760

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