Historic links to the OEIS are of the form http://www.research.att.com/~njas/sequences/A097048. These links no longer work: Neil has retired from AT&T, and in the meantime has set up the OEIS foundation. The working form these days is http://oeis.org/A097048.
Should the old-form links be changed by some automated process, or should it be left to individuals to update their links as they find them? I don't know if there's a generic policy for broken links, and I don't know, even if there is one, if the same logic should apply to the general case as to this one - an important resource for which the link pattern has changed in a predictable (and hopefully final) manner.
(I noted this when revisiting the comments for What's the simplest rational not expressible as a sum of a given number of unit fractions?, but I assume there are numerous similar references on mathoverflow.)
Hugo van der Sanden