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This is for the topswops variation ending in sorted/identity permutation.
D. E. Knuth, TAOCP, Section 220.127.116.11, Problems 107-109.
Table of n, a(n) for n=1..20.
Sequence in context: A129712 A051720 A022693 * A146478 A289500 A325276
Adjacent sequences: A174495 A174496 A174497 * A174499 A174500 A174501
Moritz Franckenstein, Nov 28 2010
a(20)=3 by Moritz Franckenstein, Apr 16 2011.