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Search: id:A080008
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| A080008 |
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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=2, r=3, I={-1,0}. |
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+0
1
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| 1, 0, 0, 1, 2, 2, 3, 5, 11, 15, 24, 40, 68, 110, 177, 290, 480, 783, 1278, 2090, 3427, 5609, 9171, 15005, 24564, 40200, 65776, 107628, 176137, 288244, 471676, 771845, 1263074, 2066938, 3382367, 5534941, 9057495, 14821891, 24254820, 39691008
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OFFSET
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0,5
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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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FORMULA
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Recurrence: a(n) = a(n-2)+a(n-3)+2*a(n-4)+2*a(n-5)-a(n-7)-a(n-9)-a(n-10) G.f.: -(x^5+x^2-1)/((x^9+x^6-x^5-x^4-x^3-x+1)*(x+1))
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CROSSREFS
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Cf. A002524-A002529, A072827, A072850-A072856, A079955-A080014.
Sequence in context: A049873 A127180 A089540 this_sequence A058697 A030427 A049907
Adjacent sequences: A080005 A080006 A080007 this_sequence A080009 A080010 A080011
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KEYWORD
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nonn
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AUTHOR
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Vladimir Baltic (baltic(AT)matf.bg.ac.yu), Feb 10 2003
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