The number of F_2 graphs on { 1, 2, ..., n } with a unique cycle of weight 1, which corresponds to the number of reflectable bases of the root system of type D_n.

A320064

The number of F_2 graphs on { 1, 2, ..., n } with a unique cycle of weight 1, which corresponds to the number of reflectable bases of the root system of type D_n.

Terms

    a(0) =0a(1) =1a(2) =16a(3) =312a(4) =7552a(5) =220800a(6) =7597824a(7) =301321216a(8) =13545271296a(9) =681015214080

External references