The directory containing the GPLed Java sources for generating Alternating
Sign Matrices is here.
Download all the files, compile them, and run "java AllASMs n" to generate
all $n x n$ ASMs classified according to the attributes $(n,k,m,p)$, where
$k$ is equal to $n$ minus the row number of the unit in the last column,
$m$ is the number of -1s, and $p$ is the inversion number of the matrix.
The program also gives a count $c$ of the number of ASMs satisfying a particular
set of attributes $(n,k,m,p)$. It is indicated in the output by "#=c."