The quadratic class number constant is a constant related to the average behavior of class numbers of real quadratic fields. It is given by Q | = | product_p[1 - 1/(p^2(p + 1))] | = | 0.881514... (OEIS A065465), where the product is over the primes p.

Artin's constant | Barban's constant | Feller-Tornier constant | Heath-Brown-Moroz constant | Murata's constant | prime products | Sarnak's constant | Taniguchi's constant | twin primes constant