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Search: id:A080003
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| A080003 |
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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={1,2}. |
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+0
1
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| 1, 1, 1, 1, 4, 8, 13, 22, 40, 77, 140, 252, 456, 834, 1525, 2775, 5049, 9195, 16760, 30536, 55617, 101304, 184544, 336193, 612424, 1115600, 2032216, 3702000, 6743761, 12284729, 22378393, 40765513, 74260396, 135276192, 246425309
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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-1)+a(n-3)+2*a(n-4)+2*a(n-5)+a(n-7)-a(n-8)-a(n-10) G.f.: -(x^5+x^3-1)/(x^10+x^8-x^7-2*x^5-2*x^4-x^3-x+1)
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CROSSREFS
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Cf. A002524-A002529, A072827, A072850-A072856, A079955-A080014.
Sequence in context: A052115 A007882 A009852 this_sequence A033016 A027008 A114997
Adjacent sequences: A080000 A080001 A080002 this_sequence A080004 A080005 A080006
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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 10 2003
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