Adn is a teeny-tiny typo with a great many alternate and legitimate meanings, mostly acronyms and abbreviations. According to Wikipedia, it can stand for at least eighteen different things, from Application Delivery Network (a suite of technologies), to ammonium dinitramide (a rocket propellant denser), to Anchorage Daily News (an Alaskan newspaper), to "any day now" (Internet slang). Perhaps my favorite one, though, is what other (dyslexic?) countries call DNA. For this reason, we got 215 hits on it in OhioLINK, though only a fraction of them were typos for the word and. If you care about this small, but all-important, part of speech and you don't mind sifting through a heap of false positives, why don't you do a search on our (possible) typo of the day and see what you can do to restore this humble connector to its rightful spelling.
(Création pour présenter les OGM, as they say in France, or, Created to introduce GMOs, as we say in the USA ... or OMG, as we all say in cyberspace! From Wikimedia Commons.)