101 distinct real numbers are written in any order
Prove that it is possible to erase 90 of them leaving a sequence of 11 numbers that are in either a strictly increasing or strictly decreasing order.
(In reply to
Sequence? by Jer)
In order to be assured of being able to leave n+1 in order, there must be n^2 + 1 numbers originally. In the present case n = 10, so that n+1 = 11 and n^2+1 = 101. For, say, being assured of 10 that are monotonic, n = 9 and you'd need 82 originally (taking away 73). Those numbers don't jibe with A241720, as the number prior to 101 should be 82.

Posted by Charlie
on 20160129 11:33:30 