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A080013
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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={0,1}.
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0
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1, 0, 0, 1, 1, 1, 1, 3, 3, 4, 6, 9, 12, 16, 24, 33, 46, 64, 91, 127, 177, 249, 349, 489, 684, 960, 1345, 1884, 2640, 3700, 5185, 7264, 10180, 14265, 19989, 28009, 39249, 54999, 77067, 107992, 151326
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,8
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COMMENTS
| Also the 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={0,-1}.
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REFERENCES
| 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
| Recurrence: a(n) = a(n-2)+a(n-3)+a(n-4)-a(n-6) G.f.: -(x^2-1)/(x^6-x^4-x^3-x^2+1)
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CROSSREFS
| Cf. A002524..A002529, A072827, A072850..A072856, A079955..A080014.
Sequence in context: A138095 A023837 A196249 * A152949 A058660 A059871
Adjacent sequences: A080010 A080011 A080012 * A080014 A080015 A080016
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KEYWORD
| nonn
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AUTHOR
| Vladimir Baltic (baltic(AT)matf.bg.ac.yu), Jan 24 2003
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