%I A136094
%S A136094 1,121,1232123,123412314213,123454321234543212345,
%T A136094 1234565432123456543212345654321,
%U A136094 1234567654321234567654321234567654321234567
%N A136094 a(n) is the shortest substring containing all the permutations of {1,
               ...,n} as (not necessarily adjacent) substrings.
%C A136094 In case of a tie we pick the earliest example.
%D A136094 P. J. Koutas and T. C. Hu, Shortest String Containing All Permutations, 
               Discrete Mathematics, Vol. 11, 1975, pp. 125-132.
%H A136094 Hu, T. C. and Koutas, P. J., <a href="http://garden.irmacs.sfu.ca/?q=op/
               smallest_universal_supersequence">Shortest Substing</a>.
%e A136094 a(4)=1234321234321 because it contains all the permutation 1234((1234)321234321), 
               1243((12)3(43)21234321), 1324((1)2(3)4321(2)3(4)321), 1342((1)2(34)3(2)1234321), 
               1423, 1432, 2134, 2143, 2314, etc. The brackets indicate where the 
               permutation is present.
%Y A136094 Sequence in context: A135825 A082215 A123179 this_sequence A053885 A068490 
               A077735
%Y A136094 Adjacent sequences: A136091 A136092 A136093 this_sequence A136095 A136096 
               A136097
%K A136094 nonn
%O A136094 1,2
%A A136094 Aniruddha Das (hi.annie.pal(AT)gmail.com), May 10 2008
%E A136094 Edited by N. J. A. Sloane (njas(AT)research.att.com), May 16 2008
%E A136094 a(4) corrected from 1234321234321 to 123412314213 by Bridget Tenner (bridget(AT)math.depaul.edu), 
               Apr 21 2009, who also confirms a(1), a(2), a(3) and a(5).
%E A136094 The entries a(6) and a(7) should be checked! - N. J. A. Sloane, May 08 
               2009