This will do it:
for k = 1 : 1000
% Get the number of failures for this row.
numFailures = randi(208);
% Get the failed indexes.
failedIndexes{k} = randperm(208, numFailures);
end
% Print to command window.
celldisp(failedIndexes);
Because it's a different number of failures each time, I used a cell array. You could use a regular array if you want - just make it big enough and set non-failures to nan or 0 or something.
