Calculate pi with Nilakantha’s series (accurate to 12 decimal places after 30,000 iterations):

#!/usr/bin/python

from decimal import *
import sys

getcontext().prec = 40

c = 0
s = Decimal(1);
pi = Decimal(3);

n = int(sys.argv[1])

for i in range(2, n * 2, 2):
pi = pi + s * (Decimal(4) / (Decimal(i) * (Decimal(i) + Decimal(1)) * (Decimal(i) + Decimal(2))))
s = -1 * s
c = c + 1
print c, (pi)