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Search: id:A080009
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| A080009 |
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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={2}. |
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+0
1
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| 1, 1, 2, 4, 11, 26, 56, 127, 288, 660, 1500, 3401, 7729, 17565, 39930, 90735, 206176, 468536, 1064750, 2419661, 5498621, 12495505, 28395889, 64529315, 146642077, 333242093, 757288191, 1720927502, 3910785158, 8887207808, 20196062308
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OFFSET
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0,3
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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-2)+2*a(n-3)+3*a(n-4)+5*a(n-5)+a(n-7)-a(n-8)-a(n-9)-a(n-10) G.f.: -(x^5+x^3-1)/(x^10+x^9+x^8-x^7-5*x^5-3*x^4-2*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: A071973 A086424 A122121 this_sequence A123432 A090899 A123440
Adjacent sequences: A080006 A080007 A080008 this_sequence A080010 A080011 A080012
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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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