Number of functions f:{1,2,...,n}->{1,2,...,n} such that every non-recurrent element has at most one preimage.
A212559
Number of functions f:{1,2,...,n}->{1,2,...,n} such that every non-recurrent element has at most one preimage.
Terms
- a(0) =1a(1) =1a(2) =4a(3) =27a(4) =244a(5) =2745a(6) =36966a(7) =580111a(8) =10399096a(9) =209672721a(10) =4696872490a(11) =115732052271
External references
- oeis: A212559