Homework & Coursework Questions

Hello Guys,For my homework I must write a shell script to do this serie,


I know that I must use the "bc" for that, but for the script's itself i have no idea,(beginner)


Can you plz just help me for have some idea?
Thanks


I wrote a program baut it does not work,

Code:

#!/bin/sh
echo "Input number"
read n
counter=0
ans=1
while [ $counter -ne $n ]
do
    ans=`expr 4*(-1/(2*$counter+1))`| bc -l 
    counter=`expr counter+1`
done

echo "the sum of the series is :-$ans"

any suggestion could help me a lot

Thanks

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