What is the value of $\sum_{i=0}^\infty $\sum_{i=0}^\infty \frac{1}{(3i+1)^2}$ frac{1}{(3i+1)^2} ?$$

Methods for other $a\pmod p$ would be helpful!, i.e., the value of $$\sum_{i=0}^\infty \frac{1}{(pi+a)^2} .$$

Thanks in advance Herman :+)

What is $\sum_{i=0}^\infty \frac{1}{(3i+1)^2}$ ?

(Excuse my nervousness to try write in LaTeX !)

Methods for other a(mod p) $a\pmod p$ would be helpful !

Thanks in advance Herman :+)

what

What is the sum i=0 to infinty of 1 over open bracket 3 times i plus one close bracket squared $\sum_{i=0}^\infty \frac{1}{(3i+1)^2}$ ?

(Excuse my nervousness to try write in LaTeX !) methods Methods for other a(mod p) would be helpful !$\sum_{i=0}^{\infty} \frac{1}{(3i+1)^2

Thanks in advance Herman :+)

what is the sum i=0 to infinty of 1 over open bracket 3 times i plus one close bracket squared ? (Excuse my nervousness to try write in LaTeX !) methods for other a(mod p) would be helpful ! $\sum_{i=0}^{\infty} \frac{1}{(3i+1)^2 Thanks in advance Herman :+)