Ultima Exodus: undead spell rng

def rng_gen(seed=0, stop=None):
    if stop is None:
        stop = seed
    a = seed
    while True:
        yield a
        a = (17*a + 23)%256
        if a == stop:
            break

def calc_fight(start):
    a = start
    mob_str = []
    count = 0
    for _ in range(8):
        a = (17*a + 23)%256 #roll for mob, 50%
        if (a * 0x80 // 256) & 0x08 != 0:
            a = (17*a + 23)%256 #roll for extra hp, d15
            mob_str += "1"
            count += 1
        else:
            mob_str += "0"
    if mob_str[3] == "0":
        mob_str[3] = "1"
        count += 1
    mobs = count
    mob_strs = [mob_str[:]]
    #18+139+77 = ~234 battle setup/teardown
    #(14+32)/2 +81 = 104 per undead cast
    #98 per mob killed
    #338 + 98X for fastest battle
    frames = 338 + 98*count
    while True:
        for i in range(8):
            if mob_str[i] == '1':
                a = (17*a + 23)%256 #roll for hit, 75%
                if a < 192:
                    count -= 1
                    a = (17*a + 23)%256 #roll for damage, 255
                    mob_str[i] = '0'
        if count == 0:
            break
        mob_strs.append(mob_str[:])
        for _ in range(count+1):
            a = (17*a + 23)%256 #roll for movement, plus extra??
        #(12+16)/2 = ~14 per turn passed *3
        #60 for monsters turn + 25 per mob
        #104+3*14+60+25*X = 206 +25X for undead recast
        frames += 206 + 25*count
    a = (17*a + 23)%256 #extra spin on victory
    return mob_strs, mobs, a, frames

rng_map = {n:i for i,n in enumerate(rng_gen())}

for i,n in enumerate(rng_gen()):
    ms, c, a, f = calc_fight(n)
    ms_out = " ".join("".join(m) for m in ms)
    score = int(f/c-140.25)
    print("{:02x} {:02x} {:02x} {:02x} {:4d} {} {:3d} {} ".format(i,n,a,rng_map[a],f,c,score,ms_out,))