%I
%S 0,0,0,0,0,1,5,19,66,218,700,2218,6997,22064,69662,220395,699090,
%T 2224114,7098773,22733498
%N Number of different strings of length n obtained from "abcde" by iteratively duplicating any substring.
%C See A137743 for more comments.
%H <a href="/index/Do#repeat">Index entries for doubling substrings</a>
%e a(k) = 0 for k<5, since no shorter string can be obtained by duplicating a substring.
%e a(5) = # { abcde }, a(6) = # { aabcde, abbcde, abccde, abcdde, abcdee },
%e a(7) = # { aaabcde, aabbcde, aabccde, aabcdde, aabcdee, ababcde, abbbcde, abbccde, abbcdde, abbcdee, abcbcde, abcccde, abccdde, abccdee, abcdcde, abcddde, abcddee, abcdede, abcdeee }
%o (PARI) A135473(13,5) /* function defined in A137743...*/
%Y Cf. A137740A137743, A135473, A137744A137748.
%K more,nonn
%O 0,7
%A _M. F. Hasler_, Feb 10 2008
%E a(14)a(19) from _Lars Blomberg_, Jan 12 2013
