Question Number 80884 by M±th+et£s last updated on 07/Feb/20
$$\underset{{u}\rightarrow{i}\infty} {{lim}}\:\underset{{k}=\mathrm{0}} {\overset{\infty} {\sum}}\frac{\left(−\mathrm{1}\right)^{{k}} \:\mathrm{6}^{{k}} \:{u}^{{k}+\mathrm{1}} }{\left(\mathrm{6}{k}+\mathrm{1}\right)!!!!!!{e}^{−{u}^{\mathrm{6}} } }\:=? \\ $$