M is the number of six-element subsets that can be chosen from the set of the first 15 positive integers so that at least three of the six numbers are consecutive.
(In reply to 2 computer solutions; the second is probably right
Only 2 consecutive inequalities by 1 need to be found for there to be 3 consecutive numbers. The program's method 2 was looking for three consecutive inequalities by 1.
Posted by Charlie
on 2016-02-09 16:29:47