jump to article number N not yet in summary

[Trent W. Buck]

Occasionally I want to jump to an old article, like

    http://article.gmane.org/gmane.emacs.bugs/15687

...from a group that has LOTS of posts.  If I tell gnus to include every
post in the summary, it takes minutes to render the summary screen.
What I'd like to do is just open it with the last 200 posts or whatever,
but say "hey please jump to article 15687".  Note that 15786 (probably)
isn't in the last 200 articles.

Is there a way to do this?  I tried to work out how
gnus-summary-refer-parent-article (^) did a similar thing, but I got a
bit overwhelmed and gave up.