Possible Duplicate:
Sum of reciprocals of squares of the form $3n+1$?
Can you help me ? $ \sum_{n=1}^{\infty}\frac{1}{(3n+1)^2} $ or how to represent it by other means ?
Possible Duplicate:
Sum of reciprocals of squares of the form $3n+1$?
Can you help me ? $ \sum_{n=1}^{\infty}\frac{1}{(3n+1)^2} $ or how to represent it by other means ?