Number of ways to use the elements of {1,..,k}, 0<=k<=2n, once each to form a collection of n (possibly empty) lists, each of length at most 2.
A105747
Number of ways to use the elements of {1,..,k}, 0<=k<=2n, once each to form a collection of n (possibly empty) lists, each of length at most 2.
Terms
- a(0) =1a(1) =4a(2) =23a(3) =216a(4) =2937a(5) =52108a(6) =1136591a(7) =29382320a(8) =877838673a(9) =29753600404
External references
- oeis: A105747