I never constructed a proof either, but it would rest on the observation that the i'th smallest disc (i=1..no_of_discs) moves every 2^i-th step in the same dire

I never constructed a proof either, but it would rest on the observation that the i'th smallest disc (i=1..no_of_discs) moves every 2^i-th step in the same direction (+1 mod 3 for odd i and -1 mod 3 for even i).