Question 15
A number from $1,2,3,\ldots,19$ is said to be a follower of a second number from $1,2,3,\ldots,19$ if either the second number is $10$ to $18$ more than the first, or the first number is $1$ to $9$ more than the second. Thus $6$ is a follower of $16,17,18,19,1,2,3,4$ and $5$. In how many ways can we choose three numbers from $1,2,3,\ldots,19$ such that the first is a follower of the second, the second is a follower of the third, and the first is also a follower of the third?