Triangular array read by rows. T(n,k) is the number of functions f:{1,2,...,n}->{1,2,...,n} whose functional digraph has exactly k nodes such that no nonrecurrent element is mapped into it. n >= 1, 1 <= k <= n.
A231536
Triangular array read by rows. T(n,k) is the number of functions f:{1,2,...,n}->{1,2,...,n} whose functional digraph has exactly k nodes such that no nonrecurrent element is mapped into it. n >= 1, 1 <= k <= n.
Terms
- a(0) =1a(1) =2a(2) =2a(3) =6a(4) =15a(5) =6a(6) =24a(7) =108a(8) =100a(9) =24a(10) =120a(11) =840a(12) =1340a(13) =705a(14) =120a(15) =720a(16) =7200a(17) =17400a(18) =15150a(19) =5466a(20) =720a(21) =5040a(22) =68040a(23) =231000a(24) =296100a(25) =171402a(26) =46921a(27) =5040a(28) =40320a(29) =705600
External references
- oeis: A231536