假设Ω(n)为正整数n的素因子个数,K=Q(-2pq),p,q互不相同的奇素数,为虚二次域,记EK=max{Ω(2x2+pq);x∈Z∩[0,pq-1]}.本文证明了Cl(K)Z/2Z Z/2Z当且仅当EK=2.
Let Ω(n) be the number of prime factors(counting multiplicity) of the positive integer n.Put EK=max{Ω(2x2+pq):x∈Z∩[0,pq-1]}.In this paper,it is proved that an imaginary quadratic field K=Q(-2pq),where p,q are different odd positive primes, has class group isomorphic to Z/2ZZ/2Z if and only if EK=2.