Number of 2Xn arrays with each row a permutation of 1..n having at least as many downsteps as the preceding row.
A221624
Number of 2Xn arrays with each row a permutation of 1..n having at least as many downsteps as the preceding row.
Terms
- a(0) =1a(1) =3a(2) =27a(3) =410a(4) =10055a(5) =353654a(6) =17052210a(7) =1075295220a(8) =86037489675
External references
- oeis: A221624