M is the number of sixelement 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.
Find M.
(In reply to
2 computer solutions; the second is probably right by Charlie)
Printing out all the positional combinations of x's for the chosen numbers shows they are all unique all 2155 of them.
It looks as if the 2155 is the right answer, and the 550 of the direct count is undercounting.

Posted by Charlie
on 20160209 16:15:26 