\( \definecolor{colordef}{RGB}{249,49,84} \definecolor{colorprop}{RGB}{18,102,241} \)
An arithmetic sequence is defined by its initial term \(u_0=8\) and a common difference \(d=4\).
Determine the index \(n\) for which the term \(u_n\) has a value of 56.
\(n=\)