I'm just curious which formula for pi is given here: <http://
docs.python.org/library/decimal.html#recipes>?
def pi():
"""Compute Pi to the current precision.
>>> print pi()
3.141592653589793238462643383
"""
getcontext().prec += 2 # extra digits for intermediate steps
three = Decimal(3) # substitute "three=3.0" for regular
floats
lasts, t, s, n, na, d, da = 0, three, 3, 1, 0, 0, 24
while s != lasts:
lasts = s
n, na = n+na, na+8
d, da = d+da, da+32
t = (t * n) / d
s += t
getcontext().prec -= 2
return +s # unary plus applies the new precision
It looks like an infinite series with term `t`, where`n` = (2k-1)^2
and `d` = d = 4k(4k+2) for k = 1... Does it have a name?
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