Seqn is a version of eqn modified for sroff and the Sanders Media 12/7
printer.  In general the defaults, etc. are similar to eqn but it
is limited to the special symbols in the Sci/Pi and greek/Math fonts.
The default font for non-special tokens is font 2 (Italic); this is 
a problem if font 2 is underlined instead of italic.  To turn off
underlining in font 2, insert ".uf 0" in the input.  ".ul" will still
produce underlined text if desired.
