Problem A. 451. (March 2008)
A. 451. Let be an upset and let
be a downset on a set S of n elements, i.e.
(a) for every we have
for all X
Y
S;
(b) for every and Y
X,
.
Prove that .
(5 pont)
Deadline expired on April 15, 2008.
Statistics:
4 students sent a solution. 5 points: Lovász László Miklós, Nagy 235 János, Tomon István, Wolosz János.
Problems in Mathematics of KöMaL, March 2008