versum.icn: Program to produce versum sequence

This program writes the versum sequence for an integer to a file of a
specified name.  If such a file exists, it picks up where
it left off, appending new values to the file.

The supported options are:

     -s i    The seed for the sequence, default 196
     -f s    Name of file to extend, no default
     -F s    Name of file, default <i>.vsq, where <i> is the
                seed of the sequence
     -t i    The number of steps to carry the sequence out to, default
                essentially unlimited
     -m i    Stop when value equals or exceeds m; default no limit

If both -f and -F are given, -f overrides.