go 220 xs = [(*220) . snd . last . fst $ every20th 220 xs]
    go cycle xs = ((*cycle) . snd . last . fst $ every20th cycle xs) : (go (cycle + 40) . snd $ every20th cycle xs)

    go c@220 xs = singleton . strength c $ every20th c xs
    go cycle xs = (strength cycle $ every20th cycle xs) : (go (cycle + 40) . snd $ every20th cycle xs)
    strength cycle = (*cycle) . snd . last . fst