Number of directed graphs of 2*n vertices each having an in-degree and out-degree of 1 such that the graph specifies a pairwise connected gift exchange with no reciprocal gifts.
A322750
Number of directed graphs of 2*n vertices each having an in-degree and out-degree of 1 such that the graph specifies a pairwise connected gift exchange with no reciprocal gifts.
Terms
- a(0) =0a(1) =0a(2) =2a(3) =48a(4) =2640a(5) =250368a(6) =34110720a(7) =6347520000
External references
- oeis: A322750