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A group of numbers: 1,0, - 1 / 3,0,1 / 5,0, - 1 / 7,0
=(-1)^((n+(1-(-1)^n)/2)/2-1)*(1+(-1)^(n+1))/(2*n)
Where ^ represents power operation, and the result is checked by Excel
one
0
-0.333333333
0
zero point two
0
-0.142857143
0
zero point one one one one one one one one one
0
-0.090909091
0
zero point zero seven six nine two three zero seven seven
0
-0.066666667
0
zero point zero five eight eight two three five two nine
0
-0.052631579
0
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