Question Number 121359 by liberty last updated on 07/Nov/20
$$\mathrm{Find}\:\mathrm{all}\:\mathrm{n}\in\mathbb{N}\:\mathrm{such}\:\mathrm{that}\:\left(\mathrm{n}+\mathrm{3}\right)^{\mathrm{n}} \:=\:\underset{\mathrm{k}=\mathrm{3}} {\overset{\mathrm{n}+\mathrm{2}} {\sum}}\:\mathrm{k}^{\mathrm{n}} \\ $$