■ある無限級数(その168)

右辺=(π/(8a^3)){tanh(aπ/2)-aπ/2・sech^2(aπ/2)}

 sinh(ix)=isinx

 cosh(ix)=cosx

 tanh(ix)=itanx

より,a→aiとおくと

=(-iπ/(8a^3)){itan(aπ/2)-aiπ/2・sec^2(aπ/2)}

=(π/(8a^3)){tan(aπ/2)-aπ/2・sec^2(aπ/2)}

 a=1/2とおくと,=π{π/2-1}

左辺=(p^2/2q)^2{{1/(p-q)-1/(p+q)}^2+{1/(3p-q)-1/(3p+q)}^2+{1/(5p-q)-1/(5p+q)}^2+・・・}

=4{{1/1-1/3}^2+{1/5-1/7}^2+{1/9-1/11}^2+・・・}

===================================