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4x4x4 upper bounds: 57 OBTM confirmed; 56 SST and 53 BT calculated.

I have replicated Shaung Chen's upper bound result of 57 moves in the OBTM (outer block turn metric), reproducing his numbers and calculating depth counts without symmetry reduction. His results are here: http://cubezzz.dyndns.org/drupal/?q=node/view/525

I have also calculated, with the same code, results in two other metrics: SST (single slice turn) and BT (block turn). The final results lower the upper bounds in these metrics to 56 and 53 (respectively).

The sequence of subsets chosen is identical to that used by Chen. The maximum distance for each stage, the sum, and the current lower bound is shown here: