Number of functions f:{1,2,...,n}->{1,2,...,n} whose cycle lengths are <= 2.
A209319
Number of functions f:{1,2,...,n}->{1,2,...,n} whose cycle lengths are <= 2.
Terms
- a(0) =1a(1) =1a(2) =4a(3) =25a(4) =218a(5) =2451a(6) =33832a(7) =554527a(8) =10535100a(9) =227790505a(10) =5525843696a(11) =148673435769
External references
- oeis: A209319