Hx=Σ(1/n-1/(n+x)) (n=1~)
を使えば,(その19)の級数は
1-1/2・H1/2
2/3-1/4・H1/4+1/4・H3/4
3/4-1/6・H1/6+1/4・H2/3
と書くことができる.
一般に
Hp/q=q/p-π/2・cotpπ/q+log2q+2Σcos2pkπ/q・logsinkπ/q (0<k<q/2)
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ω=exp(2πi/q)
Σ{1/n-1/(n+p/q)},n=1~
Σ{1/n-1/(n+p/q)}x^p+nq,n=1~
=Σω^ーkpln(1-ω^kx)-x^pln(1-x^q)+q/p・x^q
f(x)=Σω^ーkpln(1-ω^kx)
g(x)=(1-x)^pln(1-x)+q/p・x^q-x^pln(1-x^q)(1-x)
i/2+i/(ω^-p-1)=i/2・(1+ω^p)/(1-ω^p)
=i/2・(ω^p/2+ω^-p/2)/(ω^p/2-ω^-p/2)
=1/2・cotpπ/q
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