count occurrence of numbers in a sequence and return corresponding value

[michalmonday]

Now I'm even more confused to be honest.

So
X = [5,5,5,5,5]
results in:
Y = [1,1,1,1,1]

but
X = [4,4,4,4,4]
results in
Y = [3,3,3,3,3]

Another thing that is confusing me is that:
X = [1,2,3]
results in
Y = [1,2,3]

but
X = [6,6,6]
results in
Y = [4,6,7]

And in the first example it used to be:
X = [3,4,5]
resulting in
Y = [0,0,0]


What's the logic behind it?