0,8

See A137743 for more comments.

Index entries for doubling substrings

a(k) = 0 for k<6, since no shorter string can be obtained by duplication

a(6) = 1 = # { abcdef },

a(7) = 6 = # { aabcdef, abbcdef, abccdef, abcddef, abcdeef, abcdeff },

a(8) = 26 = # { aaabcdef, aabbcdef, aabccdef, aabcddef, aabcdeef, aabcdeff, ababcde,

abbbcdef, abbccdef, abbcddef, abbcdeef, abbcdeff, abcbcdef,

abcccdef, abccddef, abccdeef, abccdeff, abcdcdef,

abcdddef, abcddeef, abcddeff, abcdedef,

abcdeeef, abcdeeff, abcdefef, abcdefff }

(PARI) A135473(14, 6) /*function defined in A137743...*/

Cf. A137740-A137743, A135473, A137744-A137748.

Sequence in context: A143132 A055589 A055420 this_sequence A005022 A094811 A125107

Adjacent sequences: A137743 A137744 A137745 this_sequence A137747 A137748 A137749

more,nonn

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