Constraint randomization of continuous repeat digits

SystemVerilog
1

I want to randomize 6 bits such that no more than 2 continuously repeat digits is not allowed .
For example , 1st data = 6 (allowed)
2nd data =6 (allowed)
3rd data = 6 ( not allowed )

Any idea how should I proceed ?

Thanks

2 
I believe you want data something like this : 1,1,2,2,3,4,4,5,6,6,7...

If this is the case following can help :

  rand bit[5:0] data;
  bit [5:0] prev_data;
  bit count;

  constraint val_data{if(count) data != prev_data;}

  function void post_randomize();
    if(count) count = 0; 
    if(data == prev_data) count++;
    prev_data = data;
  endfunction

Thanks