449. Find a set of five different natural numbers in which any two numbers are coprime, and any several numbers give a composite number when summed.
449. Answer: 121, 241, 361, 481, 601. The condition is satisfied by any set of $n$ numbers $a_{i}=i \cdot n!+1$ ( $i=1,2, \ldots, n$ ). The sum of any $k$ numbers from this set is divisible by $\boldsymbol{k}$.