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A117548
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Values of n for which there exist d(1),...,d(n), each in {0,1,2} and an r in {1,2} such that Sum[d(i)d(i+k),i=1,n-k]=r (mod 3) for all k=0,...,n-1. (Such a sequence is called a very(3,r) sequence. See the link.).
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1
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OFFSET
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1,2
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COMMENTS
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Theorem. Let a be a very(3,r) sequence of length n, for r=1 or 2 and let z be a sequence of n-1 0's. Then az(2a) is a very(3,3-r) sequence of length 3n-1, where 2a denotes the sequence {2a(i) mod 3, i=1,...,n}.
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LINKS
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EXAMPLE
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For the sequence d=112102 we get Sum[d(i)d(i+k),i=1,n-k]={11,5,5,5,2,2}= {2,2,2,2,2,2) (mod 3) for k=0,...,5, so 6 is a term of the sequence.
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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