The 13th Floor Effect Below is a term from a data file in Ghostbusters: The Video Game (Stylized Versions), which is what you see in the in-game Tobin's Spirit Guide as it appears in the basement of the Firehouse, not the abbreviated version that appears in your field guide.
According to Tobin's Spirit GuideEdit
It's hard to tell which came first, the fear of the number 13 or the unfortunate incidents surrounding it. It's entirely possible the number carries some ill fate with it, but it's also possible that the negative psychic association with it turned it into a self-fulfilling prophecy of sorts. It's this reason that the 13th floor of many apartment buildings and hotels are either relabeled or left empty. This superstitious trapping draws much attention from paranormal entities who use the fear associated with it to fuel their endeavors in these locations. The wall between the physical and ethereal planes in these places can be quite thin as a result.
Triskadecaphobia is no laughing matter, but people are seldomly aware of dodecaphobia and it's insidious cousin, hexadecaphobia.
Don't worry, I don't know what Egon said either.
The art page can be found in the Hotel Sedgewick (second visit), during "The Mysterious 13th Floor" section. It is in a hallway to your right, just as the level begins.
No P.K.E. Meter scan is required.