A377135 Number of maximal chains in the poset of n-ary words of length n ordered by B covers A iff A_i <= B_i for 1 <= i <= n.
1, 1, 2, 90, 369600, 305540235000, 88832646059788350720, 14007180988362844601443040716800, 1707750599894443404262670865631874246246400000, 217425846656446788579638892849417587480505167467321080630000000
Offset: 0
Examples
For a(2) = (1,1) < (2,1) < (2,2), (1,1) < (1,2) < (2,2). For n = 3 one chain is (1,1,1) < (1,2,1) < (1,2,2) < (1,2,3) < (1,3,3) < (2,3,3) < (3,3,3).
Programs
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Maple
a:= n-> (t-> (n*t)!/t!^n)(max(n-1, 0)): seq(a(n), n=0..10); # Alois P. Heinz, Nov 27 2024
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Mathematica
a[n_]:=Product[Binomial[(n-1)*(n-i),n-1],{i,0,n-2}]; Array[a,10,0] (* Stefano Spezia, Nov 27 2024 *) -
PARI
a(n) = {if(n<1,1,(n*(n-1))!/(n-1)!^n)}
Formula
a(n) = Product_{i=0..n-2} binomial((n-1)*(n-i),n-1).
a(n) = (n*(n-1))!/(n-1)!^n for n>=1, a(0)=1. - Alois P. Heinz, Nov 27 2024
Comments