Problem 44321. Van Eck's Sequence's nth member

I don't understand why in my Matlab software it works for all the x while here it falis for x>=11

function result = VanEcksSequence(n)
A=0;
for i=1:n
if i==1
A(i+1)=0;
else
[C Chigh]=ismember(A(i),A(1:i-1));
if not(Chigh==0)
A(i+1)=i-Chigh;
else
A(i+1) = 0;
end
end
end
result = A(n);
end

@Simone Sabbatini
i dont think ur algorithm is correct. understand the sequence well..
The first term is zero. Then-
If the last term is *new* to the sequence so far then-- The next term is zero.
Otherwise:
The next term is "how far back" this last term occured previousely.