A320334 Number of ways to group the first 2*n positive integers into n pairs (xi, yi) with xi < yi, and such that the n numbers (yi - xi) mod n are all different.
1, 1, 0, 3, 12, 25, 0, 475, 5352, 17157, 0, 896535, 15083680, 68879713, 0
Offset: 0
Examples
a(3) = 3 because {(1,4), (2,6), (3,5)}, {(1,5), (2,4), (3,6)}, {(1,6), (2,5), (3,4)} are corresponding sets.
Links
- Rémy Sigrist, C++ program for A320334
Extensions
Terms computed by Rémy Sigrist, Oct 11 2018
Comments