Triangular array read by rows. T(n,k) is the number of regular elements in the semigroup of all binary relations on [n] that have rank k, n>=0, 0<=k<=n.
A363036
Triangular array read by rows. T(n,k) is the number of regular elements in the semigroup of all binary relations on [n] that have rank k, n>=0, 0<=k<=n.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =9a(5) =6a(6) =1a(7) =49a(8) =306a(9) =114a(10) =1a(11) =225a(12) =8550a(13) =26376a(14) =5256a(15) =1a(16) =961a(17) =194850a(18) =3311250a(19) =4669200a(20) =507720
External references
- oeis: A363036