Probably a No-Brainer

[hh]

You don't want to compute it but want to write it out into a field?

on mouseUp 
  put taylorsum(4,"x") into fld "OUT"
end mouseUp

function taylorsum n,x -- n is the degree, x the function argument
  put "1" into s -- or: put x &"^0/0!" into s
  repeat with i=1 to n
    put " + " & x &"^"& i &"/"& i &"!" after s
  end repeat
  return char 1 to -1 of s
end taylorsum

taylorsum(4,"x") yields --> 1 + x^1/1! + x^2/2! + x^3/3! + x^4/4!
taylorsum(4,"2") yields --> 1 + 2^1/1! + 2^2/2! + 2^3/3! + 2^4/4!