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(ïŒ-1/2^2)(1-1/3^2)(1-1/5^2)(1-1/7^2)(1-1/11^2)ã»ã»ã»Î¶(2)=1 ---(1)
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{(2^2-1)/2^2}{(3^2-1)/3^2}{(5^2-1)/5^2}{(7^2-1)/7^2}{(11^2-1)/11^2}ã»ã»ã»Î¶(2)=1 ---(2)
{(2+1)(2-1)/2^2}{(3+1)(3-1)/3^2}{(5+1)(5-1)/5^2}{(7+1)(7-1)/7^2}{(11+1)(11-1)/11^2}ã»ã»ã»Î¶(2)=1 ---(3)
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