an integer vector of length 1 or 2; if length 1,
values will be recycled to length 2; the first number used to divide
point to generate the minimum value in the sequence; the second
number is used to multiply point to generate the
maximum value in the sequence.
geo
if TRUE, seq_geo() is used to generate
the sequence; otherwise, seq_even() is used to generate
the sequence.
digits
number of significant digits in the answer; if NULL (the
default) all digits are retained.