No, a 3D array must have the same number of rows and columns for all pages. Use a cell array instead:
tjdf = cell(1, length(n));
for i = 1:length(n)
(extras)
n_input = n(i)
tjdf{i} = tjdfCoef(q12,q23,n_input,lambda,mu)
end
Cell arrays are useful, if it is meaningful to access the elements by indices and if the elements have different sizes and/or types.
