This page contains ten nested instances of the {{P1}} template, written out indirectly; five nested instances of {{P1}} are used to generate an argument, which is then passed to {{User:ais523/P1x5}} (which itself contains five nested instances of {{P1}}). This is analogous to the technique recommended at Wikipedia:Avoiding MediaWiki expansion depth limit#Optimising "recursive" depth (although on the argument half of the template call, not the name half).
This is the argument to the innermost P1.
The "highest expansion depth" for this page is also 17, considerably larger than the result obtained by simply writing all the templates out manually.