0,6

See A137743 for more comments.

Index entries for doubling substrings

a(4) = # { abcd }, a(5) = # { aabcd, abbcd, abccd, abcdd },

a(6) = # { aaabcd, aabbcd, aabccd, aabcdd, ababcd, abbbcd, abbccd, abbcdd, abcbcd, abcccd, abccdd, abcdcd, abcddd }

(PARI) A135473(12, 4)

Cf. A137740-A137743, A135473, A137745-A137748.

Sequence in context: A133409 A000746 A119915 this_sequence A027130 A027121 A025567

Adjacent sequences: A137741 A137742 A137743 this_sequence A137745 A137746 A137747

more,nonn

M. F. Hasler (MHasler(AT)univ-ag.fr), Feb 10 2008