Problem

Source: 2013 Cuba 1.4

Tags: number theory, combinatorics



A subset of the set $\{1, 2, 3, ..., 30\}$ is called delicious if it doesn't contain elements a and b such that $a = 3b$. A delicious subset It is called super delicious if, in addition to being delicious, it is verified that no delicious subset has more elements than it has. Determine the number of super delicious subsets