Y

Y = {x||x|||P(x)|}

P(x) is the power set.



Describe Y.

>>4
I don't think that's a set. For each set A one can form the set {A} with 1 (a power of 2) element. So Y contains a proper class and hence isn't a set.

(I'm not a set theorist so I'm not comletely sure this argument holds)