Răspuns:
n = 8
Explicație pas cu pas:
[tex]D_n = \{d_1,d_2,d_3,...,d_k\},\quad k \in N^* \\ \\ D_n = \{1,d_2,d_3,...,d_{k-1}, n\}\\ \\ 1+d_2+d_3+...+d_{k-1}+n = n+7 \\ d_2+d_3+...+d_{k-1} = 6 \\ \\ \text{Singura posibilitate este:}\\d_2 = 2,\quad d_3 = 4,\quad k = 4\\ \\\Rightarrow D_8 = \{1,2,4,8\}\\ \\ \Rightarrow \boxed{n = 8}[/tex]
