[tex] {3}^{n} + {3}^{n + 1} + {3}^{n + 2} + {3}^{n + 3} + {3}^{n + 4} [/tex]
[tex] {3}^{n} (1 + {3}^{1} + {3}^{2} + {3}^{3} + {3}^{4} )[/tex]
[tex] {3}^{n} (1 + 3 + 9 + 27 + 81)[/tex]
[tex] {3}^{n} \times 121[/tex]
[tex] {3}^{n} \times 11 \times 11[/tex]
sigur divizibil cu 11
