λN.λx.
{
  sumi ← λn.λN.λf. (+)/ₒ 0 (f'1 (irange n N 1));
  fact ← [(*)/ₒ 1 (frange 1 x (⌊x))];
  mkIx ← λn. (x^n)%(fact (𝑖n));
  sumi 0 N mkIx
}