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Search: id:A079967
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| A079967 |
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Number of permutations satisfying -k<=p(i)-i<=r and p(i)-i not in I, i=1..n, with k=1, r=5, I={4}. |
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+0
1
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| 1, 1, 2, 4, 8, 15, 30, 58, 113, 220, 429, 835, 1627, 3169, 6173, 12024, 23422, 45623, 88869, 173107, 337194, 656817, 1279409, 2492150, 4854439, 9455922, 18419114, 35878442, 69887326, 136132954, 265172275, 516526919, 1006138588, 1959849178
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OFFSET
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0,3
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COMMENT
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Number of compositions (ordered partitions) of n into elements of the set {1,2,3,4,6}.
Note that the number of compositions of n with parts in N which avoid the pattern 221 (see Heubach/Mansour) is not this sequence but A134044.
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REFERENCES
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D. H. Lehmer, Permutations with strongly restricted displacements. Combinatorial theory and its applications, II (Proc. Colloq., Balatonfured, 1969), pp. 755-770. North-Holland, Amsterdam, 1970.
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LINKS
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S. Heubach and T. Mansour, Enumeration of 3-letter patterns in combinations
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FORMULA
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Recurrence: a(n) = a(n-1)+a(n-2)+a(n-3)+a(n-4)+a(n-6) G.f.: -1/(x^6+x^4+x^3+x^2+x-1)
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CROSSREFS
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Cf. A002524-A002529, A072827, A072850-A072856, A079955-A080014.
Sequence in context: A091865 A065494 A134044 this_sequence A018088 A018089 A124312
Adjacent sequences: A079964 A079965 A079966 this_sequence A079968 A079969 A079970
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KEYWORD
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nonn
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AUTHOR
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Vladimir Baltic (baltic(AT)galeb.etf.bg.ac.yu), Feb 19 2003
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