Let p be an odd prime number, and pn0{p^{n_0}} the highest power of p dividing 2 p−1 − 1. Let _boxclose_boxclose(_p^n+1){K_n={bf Q}(zeta_{p^{n+1}})} and Ln,j=Kn+(z2j+2){L_{n,j}=K_n^+(zeta_{2^{j+2}})} for j ≥ 0. Let hn*{h_n^*} be the relative class number of K n , and h n,j the class number of L n,j , respectively. Let n be an integer with n ≥ n 0. We prove that if the ratio hn*/hn-1*{h_n^*/h_{n-1}^*} is odd, then h n,j /h n−1,j is odd for any j ≥ 0.
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