import math  
f = lambda x, a, b, c, d: a / (1 + math.exp(-b - c * x - d * x**2))

def calc_and_save(a, b, c, d, filename="results.txt"):
    xs = [x for x in range(-20, 21, 2)]
    values = [f(x, a, b, c, d) for x in xs]

    with open(filename, "w", encoding="utf-8") as file:
        for i, val in enumerate(values, start=1):
            file.write(f"{val:.6f}")
            if i % 3 == 0:
                file.write("\n")
            else:
                file.write(" ")