Preallocate a cell array, define each cell element accordingly and use indexing to access the data -
%Number of arrays
n = 10;
%Preallocating a cell array
out = cell(n,1);
for k=1:n
out{k} = ones(1,k);
end
%See the output
out
%Access an array via indexing e.g. 3rd array
out{3}
