Henry Ernest Dudeney/Puzzles and Curious Problems/315 - Arranging the Dominoes

by : $315$

 * Arranging the Dominoes
 * The number of ways the set of $28$ dominoes may be arranged in a straight line, in accordance with the original rule of the game,
 * left to right and right to left, in any arrangement counting as different ways,
 * is $7 \, 959 \, 229 \, 931 \, 520$.


 * After discarding all dominoes bearing a $5$ or a $6$, how many ways may the remaining $15$ dominoes be so arranged in a line?