Message from the system at Berkeley, October 2009:

Oct  2: Warning: Due to a known bug, the default Linux document viewer
        evince prints N*N copies of a PDF file when N copies requested.
        As a workaround, use Adobe Reader acroread for printing multiple
        copies of PDF documents, or use the fact that every natural number
        is a sum of at most four squares.

For confirmation that this is real, see here and here.

For another story about mathematics and software bugs, see here.

Note that this is Lagrange’s four-square theorem, not to be confused with other theorems also called Lagrange’s theorem. And Dario Alpern has a great webpage that decomposes an integer as a sum of squares, including a proof.