Question 150
A set $T$ of integers is called *orensano* if there are integers $a \lt b \lt c$ such that $a, c \in T$ and $b \notin T$.
Find the number of orensano subsets $T$ of $\{1, 2, \dots, 2019\}$.
Find the number of orensano subsets $T$ of $\{1, 2, \dots, 2019\}$.