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A137739
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Number of different strings of length n+6 obtained from "123...n" by iteratively duplicating any substring.
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4
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1, 64, 355, 1014, 2218, 4217, 7343, 12018, 18767, 28233, 41193, 58575, 81476, 111181, 149183, 197204, 257217, 331469, 422505, 533193
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| See A137743 for comments and examples.
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LINKS
| Index entries for doubling substrings
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FORMULA
| a(n)=1/720*(n+9)*(n^5+36*n^4+451*n^3+1716*n^2-380*n-8880)-1 for n>4.
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PROG
| (PARI) A137739(n)=if(n<2, 1, n=A135473(n+6, n); n[ #n]) /* function A135473 defined in A137743 */
(PARI) A137739(n)=if(n>4, n*(n*(n*(n*(n+45)+775)+5775)+15064)-12300)/7!-112, [1, 64, 355, 1014][n])
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CROSSREFS
| Cf. A137740-A137743, A135473, A137744-A137748.
Sequence in context: A186441 A016779 A061102 * A017486 A105918 A188840
Adjacent sequences: A137736 A137737 A137738 * A137740 A137741 A137742
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KEYWORD
| nonn
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AUTHOR
| M. F. Hasler (www.univ-ag.fr/~mhasler), Feb 10 2008
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