import numpy as np
from math import exp, log

xs = [-1.428086671,
-0.357021668,
-0.158676297,
-0.089255417,
-0.057123467,
-0.039669074,
-0.029144626,
-0.022313854,
-0.0176307,
-0.014280867,
-0.011802369,
-0.009917269,
-0.008450217,
-0.007286156,
-0.006347052,
-0.005578464
]
def linear_regression(xs, ys):
    n = len(xs)
    mx, my = sum(xs) / n, sum(ys) / n
    a = sum((x - mx) * (y - my) for x, y in zip(xs, ys)) / sum((x - mx)**2 for x in xs)
    b = my - a * mx
    return a, b
sgn = -1
XS = [log(k) for k in range(13, 16)]
print([xs[k] / xs[k - 1] for k in range(13, 16)])
YS = [log(abs(xs[k])) for k in range(13, 16)]
z = linear_regression(XS,YS)
s = sum(xs)
p = 1+z[0]
tail =  - sgn * exp(z[1]) * 15.5**p / p
print(s, s + tail)