Let S be a regular semigroup and let ρ be a congruence relation on S. The kernel of ρ, in notation $\ker \rho$, is the union of the idempotent ρ-classes. The trace of ρ, in notation tr ρ, is the ...

Jonathan W. Tanner, Samuel S. Wagstaff, Jr. We prove a new congruence for computing Bernoulli numbers modulo a prime. Since it is similar to Vandiver's congruences but has fewer terms, it may be used ...