trouble with some python coding to estimate pi

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Im trying to estimate pi, the first term in the series is correct the second is -1 instead of -4/3. then just zeros im sure my closed form for the sequence is right i just cant figure out where im going wrong...

#premise for this problem:
#working from the starting point of a tayler expansion of 1/(1-x) 
#Start with 1/(1+w) = 1 - w + w2 - w3 + ...
#Now substitute x2 for w:
#1/(1+x2) = 1 - x2 + x4 - x6 + ...
#Then integrate both sides (from x=0 to x=y):
#arctan y = y - y3/3 + y5/5 - y7/7 +...
#and plug in y=1, to get
# Pi/4 = 1 - 1/3 + 1/5 - 1/7 + ...
from math import *
import numpy as np

n= 100 #define range
x= 1   #define range
series = [] # define our series expantion Pi/4 = 1 - 1/3 + 1/5 - 1/7 + ...
for u in range(0,n):
    if ((u %2)==0): #if even r=positive
        r=1
    else:
        r=-1        #else r=negitive
    d= (1+(u*2))
    value = ((4//d)*r)
    series.append(value)

sumseries= sum(series) #sum the series
print (sumseries)
print 'error in pi is', (sumseries/pi)*100, '%'
print series 
0

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