A137744 - OEIS

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A137744

Number of different strings of length n obtained from "abcd" by iteratively duplicating any substring.

0, 0, 0, 0, 1, 4, 13, 40, 119, 348, 1014, 2966, 8726 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,6`
	COMMENTS	`See A137743 for more comments.`
	LINKS	`Index entries for doubling substrings`
	EXAMPLE	`a(4) = # { abcd }, a(5) = # { aabcd, abbcd, abccd, abcdd },` `a(6) = # { aaabcd, aabbcd, aabccd, aabcdd, ababcd, abbbcd, abbccd, abbcdd, abcbcd, abcccd, abccdd, abcdcd, abcddd }`
	PROG	`(PARI) A135473(12, 4)`
	CROSSREFS	`Cf. A137740-A137743, A135473, A137745-A137748.` `Sequence in context: A000746 A191132 A119915 * A027130 A027121 A025567` `Adjacent sequences: A137741 A137742 A137743 * A137745 A137746 A137747`
	KEYWORD	`more,nonn`
	AUTHOR	`M. F. Hasler (www.univ-ag.fr/~mhasler), Feb 10 2008`

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Last modified February 14 18:47 EST 2012. Contains 205663 sequences.