The starting point of this question is the observation that the smallest positive integers $a,b,c$ satisfying

$$\frac{a}{b+c} + \frac{b}{a+c} + \frac{c}{a+b} = 4$$

are [absurdly high][1], namely <sub>$$(154476802108746166441951315019919837485664325669565431700026634898253202035277999,$$ $$36875131794129999827197811565225474825492979968971970996283137471637224634055579
,$$ $$
4373612677928697257861252602371390152816537558161613618621437993378423467772036)
.$$</sub> This leads to the following general question: Is the set $C\subseteq {\mathbb N}$ defined by $$ C = \{n\in\mathbb{N}\setminus\{0\}: (\exists a,b,c \in\mathbb{N}\setminus\{0\}):\frac{a}{b+c} + \frac{b}{a+c} + \frac{c}{a+b} = n\}$$
computable? (As user [Watson][2] points out in the comment section below, $C$ contains no odd numbers. It would also be great to see an even number $\geq 6$ not contained in $C$.)


  [1]: https://web.archive.org/web/20170813162605/https://plus.google.com/+johncbaez999/posts/Pr8LgYYxvbM
  [2]: https://mathoverflow.net/users/84923/watson