%I A013927
%S A013927 0,2,5,10,15,23
%N A013927 Begin with 2n cards in n piles of 2, the piles being {1,1},{2,2},{3,3},
               ...,{n,n}. How many transpositions of adjacent (single) cards are 
               needed to reverse the order of the piles?
%D A013927 Graham Brightwell, Michael Littman and Peter Winkler (pw(AT)research.bell-labs.com), 
               unpublished.
%Y A013927 Sequence in context: A125622 A080551 A008822 this_sequence A163059 A099738 
               A117582
%Y A013927 Adjacent sequences: A013924 A013925 A013926 this_sequence A013928 A013929 
               A013930
%K A013927 nonn
%O A013927 1,2
%A A013927 N. J. A. Sloane (njas(AT)research.att.com).