a(n) is the number of pairings of the first 2*k positive integers into k pairs (xi, yi) such that the k numbers (xi + yi) mod k are all different where k = 2*n + 1.
A320333
a(n) is the number of pairings of the first 2*k positive integers into k pairs (xi, yi) such that the k numbers (xi + yi) mod k are all different where k = 2*n + 1.
Terms
- a(0) =1a(1) =9a(2) =145a(3) =4641a(4) =231417a(5) =16770369a(6) =1671395713
External references
- oeis: A320333