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Search: id:A122536
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| A122536 |
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Number of binary sequences of length n with no initial repeats. |
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+0
4
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| 2, 2, 4, 6, 12, 20, 40, 74, 148, 286, 572, 1124, 2248, 4460, 8920, 17768, 35536, 70930, 141860, 283440, 566880, 1133200, 2266400, 4531686, 9063372, 18124522, 36249044, 72493652, 144987304, 289965744
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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An initial repeat of a string S is a number k>=1 such that S[i]=S[i+k] for i=0..k-1. In other words, the first k symbols are the same as the next k symbols, e.g. ABCDABCDZQQ has an initial repeat of size 4.
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LINKS
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Guy P. Srinivasan, Java program for this sequence and A003000
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EXAMPLE
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a(4)=6: 0100, 0110, 0111, 1000, 1001 and 1011.
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CROSSREFS
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Cf. A003000.
Sequence in context: A030435 A063886 A003000 this_sequence A128209 A052953 A074028
Adjacent sequences: A122533 A122534 A122535 this_sequence A122537 A122538 A122539
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KEYWORD
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more,nonn
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AUTHOR
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Guy P. Srinivasan (srinivgp(AT)gmail.com), Sep 18 2006
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