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##Z(\lambda)=\frac{1}{\sqrt{2\pi}}\int^{\infty}_{-\infty}d\phi\ \exp\{-\frac{1}{2}\phi^{2}-\frac{\lambda}{4!}\phi^{4}\}.##

It can be shown that

##Z(\lambda)=\sum\limits_{n=0}^{\infty}c_{n}\lambda^{n},##

where ##c_{n}=\frac{(-1)^{n}(2n-1)!!}{(4!)^{n}n!}.##

Can we instead propose a set of Feynman rules to compute the ##c_n##'s, or can Feynman rules only be written down for the correlation functions of the theory?