A more effective pseudoprime test than the simpler Fermat test. A number N is called an Euler pseudoprime to base b if b^(N-1)/2 =(b/N) (mod N). (Here (b/N) is the Jacobi symbol.) This test is also called the Solovay-Strassen test for its original proposers. If an integer is an Euler pseudoprime it is also a Fermat pseudoprime.