SpecialSequence AIME
2015

Problem - 61
Let $S$ be the set of all ordered triple of integers $(a_1,a_2,a_3)$ with $1 \le a_1,a_2,a_3 \le 10$. Each ordered triple in $S$ generates a sequence according to the rule $a_n=a_{n-1}\cdot | a_{n-2}-a_{n-3} |$ for all $n \ge 4$. Find the number of such sequences for which $a_n=0$ for some $n$.