`P``=``1``+``3``+``3²``+``3³``+``....``+`$3^{100}$+$3^{101}$
`=``(``1``+``3``+``3²``)``+``(``3³``+`$3^{4}$+$3^{5}$)+....+($3^{99}$+$3^{100}$+$3^{101}$)
`=``(``1``+``3``+``9``)``+``3³``.``(``1``+``3``+``9)``+``......``+`$3^{99}$`.``(``1``+``3``+``9``)`
`=``13``+``3³``.``13``+``......``+`$3^{99}$`.``13`
`=``13``.``(``1``+``3³``+``....``+``$3^{99}$`)` ⋮ `13`
Vậy `P` ⋮ `13`