Question: Generating list of matrices

Hello, I'm trying to enumerate matrices, each P [j] with j = 1,2,3 ... n-1. , and also can also the value of its elements with P [j] (r, k) for example.
n:=4;

for j from 1 to n-1 do 
P[j]:=Matrix(n); 
for l from 1 to n do
P[j](l,l):=1;  
end do; 
end do;
Error, invalid operator parameter name

Regards.

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