Problem:

Find the coefficient of the third term in the series expansion of the following function around 3:

$\sin (x)-e^{-7 x/2}$

import math

from sympy import *
from sympy.abc import x

f = S(sin(x)-math.e**(-7*x/2))
series = f.series(x, 3, None)
for i, term in enumerate(series):
    if i == 3: print(term)
    elif i > 3: break
print(0)

