Number of 4-element proper antichains of an n-element set.
A051304
Number of 4-element proper antichains of an n-element set.
Terms
- a(0) =0a(1) =0a(2) =0a(3) =0a(4) =5a(5) =780a(6) =41545a(7) =1442910a(8) =39400305a(9) =923889960a(10) =19550316665a(11) =384954289170
External references
- oeis: A051304