1101 in binary is decimal number 13. In ASCII, this translates to the [CR] "character". CR = Carriage Return, which returns the cursor (or printer head) to the beginning of the current line. To advance the cursor to the beginning of the next line, you have to use a CRLF (Carriage Return, Line Feed), which is 2 ASCII values, [13] and [10]. The [ENTER] key on the keyboard is essentially a combination of these 2 characters.

So, in essence, this bill's serial number (if implemented on the US Government Printing Office's printing press) would cause the serial number printer to jump to the start of the line and then to the same spot immediately after, and since nothing follows, it would effectively cause the number you're reading to never print. Ooh, soak that one in for a few hours, eh?

You can all say it now... "NERRRRRRRRRRRRD!!!"