Goldbach's conjecture

Goldbach's conjecture asserts that all positive even integers greater or equal to 4 can be expressed as the sum of two primes.

Pi by Leonhard Euler

(Pi x Pi) / 6 = 1 / (1 x 1) + 1 / (2 x 2) + 1 / (3 x 3) + 1 / (4 x 4) + ... + 1 / (n x n) + ...

Pi by Gottfried W. Leibniz

Pi / 8 = 1 / (1 x 3) + 1 / (5 x 7) + 1 / (9 x 11) + ...

Pi by John Wallis

Pi / 2 = (2 x 2 x 4 x 4 x 6 x 6 x ...) / (3 x 3 x 5 x 5 x 7 x 7 x ...)