■ある無限級数(その119)

[1]πが出現する無限級数

 1+1/2^2+1/3^2+1/4^2+・・・=π^2/6

 1+1/2^4+1/3^4+1/4^4+・・・=π^4/90

 1−1/2^2+1/3^2−1/4^2+・・・=π^2/12

 1−1/2^4+1/3^4−1/4^4+・・・=7π^4/720

 1−1/3^3+1/5^3−1/7^3+・・・=π^3/32

 1−1/3^5+1/5^5−1/7^5+・・・=5π^5/1536

 1+1/3^2+1/5^2+1/7^2+・・・=π^2/8

 1+1/3^4+1/5^4+1/7^4+・・・=π^4/96

 1/0.5^2+1/1.5^2+1/2.5^2+1/3.5^2+・・・=π^2/2

 1/0.5^2+1/1^2+1/1.5^2+1/2^2+・・・=2π^2/3

[2]ゼータ関数が出現する無限級数

 1/ζ(s)

=(1−1/2^2)(1−1/3^s)(1−1/5^2)(1−1/7^s)・・・

=Σμ(n)/n^s

=1−1/2^s−1/3^s−1/5^s+1/6^s−1/7^s+1/10^s−1/11^s−・・・

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[参]若原龍彦「美しい無限級数」プレアデス出版

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