lehmer.py

def lehmer_merge(clip, lowpass=lambda i: core.std.BoxBlur(i, hradius=3, vradius=3, hpasses=2, vpasses=2)):
    count = len(clip)
    expr = ""

    for i in range(count):
        expr += f"src{i} src{count + i} - D{i}! "

    for v in range(2):
        for i in range(count):
            expr += f"D{i}@ {v + 2} pow "
        expr += "+ " * (count - 1) + f"P{v}! "

    for i in range(count):
        expr += f"src{count + i} "
    expr += "+ " * (count - 1) + f"{count} / "

    expr += "P0@ 0 = 0 P1@ P0@ / ? +"

    blur = [lowpass(i) for i in clip]
    return core.akarin.Expr(clip + blur, expr)