Question 175
Consider the set $A = \{1, 2, 3, \dots, 2017\}$. Determine the number of three element subsets $B \subset A$, which satisfy the following conditions simultaneously:
a) at least two elements in the set $B$ are consecutive positive integers;
b) there is an $a \in B$, such that $3a \in B$.
a) at least two elements in the set $B$ are consecutive positive integers;
b) there is an $a \in B$, such that $3a \in B$.