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Search: id:A115562
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| A115562 |
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a(n) = number of distinct square-free ternary (cyclic) sequences uniquely containing every possible length-n substring. |
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+0
1
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OFFSET
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1,1
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COMMENT
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Sometimes called "square-free de Bruijn sequences" Two such sequences are distinct if they are not cyclic permutations of each other. Open: do any such ternary sequences exist for n>4 ?
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EXAMPLE
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a(2) = 3 because the following 3 sequences contain each length-2 substring {01,02,10,12,20,21} while avoiding any square {00,11,22}, and are all distinct from each other:
010212
012021
012102
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CROSSREFS
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Sequence in context: A049268 A004179 A122830 this_sequence A127468 A058301 A097287
Adjacent sequences: A115559 A115560 A115561 this_sequence A115563 A115564 A115565
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KEYWORD
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hard,nonn
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AUTHOR
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Jim Nastos (nastos(AT)gmail.com), Mar 11 2006
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