[tex]a)4!=1\cdot2\cdot3\cdot4=24 \\ b)1!=1 \\ 2!=2 \\ 3!=6 \\ 4!=24 \\ 5!=120\leftarrow asta\ e\ bun \\ c)1!+2013=2014\leftarrow\ nu\ e\ patrat\ perfect \\ 2!+2013=2015\leftarrow nu\ e\ patrat\ perfect \\ 3!+2013=2019\leftarrow nu\ e\ patrat\ perfect \\ 4!+2013=2037\leftarrow nu\ e\ patrat\ perfect \\ 5!+2013=2133\leftarrow nu\ e\ patrat\ perfect [/tex]