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Search: id:A103580
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| A103580 |
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Number of non-empty subsets S of {1,2,3,...,n} that have the property that no element x of S is a nonnegative integer linear combination of elements of S-{x}. |
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2
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| 1, 2, 4, 6, 11, 15, 26, 36, 57, 79, 130, 170, 276, 379, 579, 784, 1249, 1654, 2615, 3515, 5343, 7256, 11352, 14930, 23203, 31378, 47510, 63777, 98680, 130502, 201356, 270037, 407428, 548089, 840170, 1110428, 1701871, 2284324, 3440336, 4601655
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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Sergey Kitaev, Independent Sets on Path-Schemes, Journal of Integer Sequences, Vol. 9 (2006), Article 06.2.2.
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EXAMPLE
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a(4) = 6 because the only permissible subsets are {1}, {2}, {3}, {4}, {2,3}, {3,4}.
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CROSSREFS
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Cf. A085489, A139384.
Sequence in context: A108868 A156913 A138461 this_sequence A094866 A072951 A062766
Adjacent sequences: A103577 A103578 A103579 this_sequence A103581 A103582 A103583
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KEYWORD
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nonn
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AUTHOR
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Jeffrey Shallit (shallit(AT)graceland.uwaterloo.ca), Mar 23 2005
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EXTENSIONS
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More terms from David Wasserman (dwasserm(AT)earthlink.net), Apr 16 2008
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