where the product is over odd primes (all primes except 2) and where the signs in the denominators depends on whether the prime is of the form 4k + 3 (+ sign) or 4k + 1 (
where the product is over odd primes (all primes except 2) and where the signsin the denominators depends on whether the prime is of the form 4k + 3 (+ sign)or 4k + 1 (