a(n) is the number of Klein four orbits of permutations generated by the operations of inverse permutation and conjugation by w_0 = [n, n-1, ..., 1].

A300931

a(n) is the number of Klein four orbits of permutations generated by the operations of inverse permutation and conjugation by w_0 = [n, n-1, ..., 1].

Terms

    a(0) =1a(1) =1a(2) =2a(3) =4a(4) =13a(5) =45a(6) =230a(7) =1388a(8) =10558a(9) =92126a(10) =912908a(11) =9998008a(12) =119831996a(13) =1557050972a(14) =21795929320a(15) =326923928048

External references