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Search: id:A053623
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| A053623 |
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Number of distinct non-extendable sequences {x(1),x(2),...,x(k)} such that each x(i) is in {1,2,...,n} and x(j) AND x(i)<>x(j) for i=2,..k, j=1,..,i-1. |
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+0
2
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| 1, 2, 4, 14, 38, 126, 252, 1662, 7180, 39430, 111064, 803876, 2863992, 12123360, 24246720, 329012784
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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Related to Mathematical Recreations, Scientific American, March 2000.
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EXAMPLE
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a(3)=4, since the allowable sequences are {1,2}, {2,1}, {3,1,2}, {3,2,1}. ({1,3} is not allowed because 1 AND 3 = 01 AND 11 (base 2) = 1, and {3,1} is not allowed because it can be extended to {3,1,2}.)
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CROSSREFS
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Cf. A054668.
Sequence in context: A135960 A006611 A007462 this_sequence A035010 A055540 A006252
Adjacent sequences: A053620 A053621 A053622 this_sequence A053624 A053625 A053626
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KEYWORD
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nonn
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AUTHOR
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John W. Layman (layman(AT)math.vt.edu), Mar 21 2000
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