Question Number 30440 by abdo imad last updated on 22/Feb/18
$${if}\:\:\:\left(\sum_{{n}\geqslant\mathrm{1}} \:\:\:\frac{\left(−\mathrm{1}\right)^{{n}−\mathrm{1}} }{{n}^{{x}} }\right)^{\mathrm{2}} =\:\sum_{{n}} \:\:{c}_{{n}\:} \left({x}\right)\:\:{find}\:{c}_{{n}} \left({x}\right). \\ $$