Number of rooted trees with 4 nodes of disjoint sets of labels with union {1..n}. If a node has an empty set of labels then it must have at least two children.
A005174
Number of rooted trees with 4 nodes of disjoint sets of labels with union {1..n}. If a node has an empty set of labels then it must have at least two children.
Terms
- a(0) =0a(1) =0a(2) =10a(3) =124a(4) =890a(5) =5060a(6) =25410a(7) =118524a(8) =527530a(9) =2276020a(10) =9613010a(11) =40001324a(12) =164698170a(13) =672961380a(14) =2734531810a(15) =11066546524a(16) =44652164810a(17) =179768037140a(18) =722553165810
External references
- oeis: A005174