real procedure He(n, X); comment This procedure computes the Hermite polynomial Hn(X) = (-1)^n * exp(X^2) * (d^n/dX^n(exp(-X^2)) for any given real argument X, and any order, n, by the recursion formula below; integer n; real X; begin real a, b, c; integer i; a ≔ 1; b ≔ 2×X; if n = 0 then c ≔ a else if n = 1 then c ≔ b else for i ≔ 1 step 1 until n - 1 do begin c ≔ 2 × X × b - 2 × i × a; a ≔ b; b ≔ c end; He ≔ c end;