Seventeen integers $a_1,a_2,a_3,\dots ,a_{17}$ are arranged in order on a number line. The integers are equally spaced and have the property that
$1\le a_1\le 5$, $15\le a_2\le 19$, and $197\le a_{17}\le 205$.
What is the sum of digits of $a_{15}$?