Search: id:A137748
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%I A137748
%S A137748 0,0,0,0,0,0,0,0,1,8,43,196,814,3188,12018
%N A137748 Number of different strings of length n obtained from "abcdefgh" by iteratively 
               duplicating any substring.
%C A137748 See A137743 for more comments.
%H A137748 <a href="Sindx_Do.html#repeat">Index entries for doubling substrings</
               a>
%e A137748 a(k) = 0 for k<8, since no shorter string can be obtained by duplication 
               of substrings.
%e A137748 a(8) = 1 = # { abcdefgh },
%e A137748 a(9) = 8 = # { aabcdefgh, abbcdefgh, abccdefgh, abcddefgh, abcdeefgh, 
               abcdeffgh, abcdefggh, abcdefghh },
%e A137748 a(10) = (8+1)*(8+2)/2-2 = 43: for each letter we have one string of the 
               form aaabcdefgh;
%e A137748 for each 2-element subset {a,b}, {a,c},... we have the string with each 
               of these two letters duplicated (i.e. aabbcdefgh, aabccdefgh,...),
%e A137748 and for each of ab,bc,cd,...,gh we have the string with this substring 
               duplicated (ababcdefgh,...,abcdefghgh).
%o A137748 (PARI) A135473(14,8) /*function defined in A137743*/
%Y A137748 Cf. A137740-A137743, A135473, A137744-A137747.
%Y A137748 Sequence in context: A036647 A000429 A055853 this_sequence A005024 A094865 
               A122880
%Y A137748 Adjacent sequences: A137745 A137746 A137747 this_sequence A137749 A137750 
               A137751
%K A137748 more,nonn
%O A137748 0,10
%A A137748 M. F. Hasler (MHasler(AT)univ-ag.fr), Feb 10 2008

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