Consider a clock face with 2*n "hours" marked around the dial; a(n) = number of ways to match the even hours to the odd hours, modulo rotations and reflections.

A357442

Consider a clock face with 2*n "hours" marked around the dial; a(n) = number of ways to match the even hours to the odd hours, modulo rotations and reflections.

Terms

    a(0) =1a(1) =1a(2) =3a(3) =5a(4) =17a(5) =53a(6) =260a(7) =1466a(8) =10915a(9) =93196a(10) =917898a(11) =10015299a(12) =119914982a(13) =1557364352a(14) =21797494987a(15) =326930305166

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