12. When $n$ takes all the values in $1,2,3, \cdots, 2015$, how many numbers of the form $3^{n}+n^{3}$ are divisible by 7?
【Answer】288 $1, 6, 1, 6, 6, 0$, then the total period is 42, list
$$
2015 \div 42=47 \cdots \cdots 41, \quad 47 \times 6+6=288
$$