MATLAB: Could anyone help me to solve the issue

bell

the command executes and gives the result
temp = arrayfun(@(z) feval(symengine, 'combinat::bell', z), [ 4], 'uniform', 0)
output = vertcat(temp{:})
but i want to get view the result of 4 say for example(a,b,c,d).How to view all 15 possible combinations . Could anyone help me on this.