$\forall$$T$:Type, $L$:($T$ List).
\\[0ex](0 $<$ $\parallel$$L$$\parallel$) $\Rightarrow$ no\_repeats($T$;$L$) $\Rightarrow$ ($\forall$$a$:$T$. adjacent($T$;$L$;last($L$);$a$) $\Leftarrow\!\Rightarrow$ False)