|
%I #20 May 12 2023 12:05:54
%S 0,2,5,10,15,23,31,40
%N 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%D Graham Brightwell, Michael Littman and Peter Winkler (pw(AT)research.bell-labs.com), unpublished.
%H Bert Dobbelaere, <a href="/A013927/a013927.txt">Example solution for a(8)</a>
%e From _Bert Dobbelaere_, Jan 19 2020: (Start)
%e a(3) = 5:
%e Start: {1,1} {2,2} {3,3}
%e Step 1: {2,1} {1,2} {3,3}
%e Step 2: {2,1} {3,2} {1,3}
%e Step 3: {2,3} {1,2} {1,3}
%e Step 4: {2,3} {3,2} {1,1}
%e Step 5: {3,3} {2,2} {1,1}
%e (End)
%K nonn,more
%O 1,2
%A _N. J. A. Sloane_
%E a(7)-a(8) from _Bert Dobbelaere_, Jan 19 2020
|
