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A080014
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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=2, I={1}.
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77
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1, 1, 1, 3, 6, 10, 18, 35, 65, 119, 221, 412, 764, 1416, 2629, 4881, 9057, 16807, 31194, 57894, 107442, 199399, 370065, 686799, 1274617, 2365544, 4390184, 8147680, 15121161, 28063153, 52082017, 96658283, 179386750, 332921362, 617864098
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OFFSET
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0,4
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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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Table of n, a(n) for n=0..34.
Vladimir Baltic, On the number of certain types of strongly restricted permutations, Applicable Analysis and Discrete Mathematics Vol. 4, No 1 (2010), 119-135
Index entries for linear recurrences with constant coefficients, signature (1,1,1,1,-1,-1).
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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-5)-a(n-6).
G.f.: -(x^2-1)/(x^6+x^5-x^4-x^3-x^2-x+1).
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PROG
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(PARI) Vec(-(x^2-1)/(x^6+x^5-x^4-x^3-x^2-x+1)+O(x^99)) \\ Charles R Greathouse IV, Jun 12 2015
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CROSSREFS
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Cf. A002524-A002529, A072827, A072850..A072856, A079955..A080014.
Sequence in context: A261631 A029864 A075111 * A132274 A253768 A091714
Adjacent sequences: A080011 A080012 A080013 * A080015 A080016 A080017
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KEYWORD
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nonn,easy
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AUTHOR
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Vladimir Baltic, Jan 24 2003
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STATUS
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approved
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