Find the number of permutations of (1,2,3...n) possessing the following feature:
The number n is the only local maximum e.g. 123465, 123564, 654321,
as opposed to 651432, 261354.
(In reply to error in "official solution"
by Steve Herman)
It is definitely better, but not an error. Trying to make it short nothing was said about the nature of k, but it is actually not a constant number, it is k(n) which is equivalent to f(n).
Unfortunately there is no way to correct the official solution, and
your post is most helpful to someone who missed my intentions.
Thank you for your remark.
Edited on October 2, 2015, 9:36 pm