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Search: id:A079991
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| A079991 |
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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=3, r=3, I={-1,1}. |
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+0
1
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| 1, 1, 1, 2, 5, 13, 29, 58, 124, 280, 632, 1406, 3101, 6851, 15217, 33846, 75181, 166823, 370177, 821760, 1824620, 4051056, 8993220, 19964240, 44320545, 98393849, 218438981, 484939834, 1076573833, 2390015565, 5305896445, 11779231650
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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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FORMULA
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Recurrence: a(n) = 2*a(n-1)+3*a(n-4)+a(n-6)-8*a(n-7)-a(n-8)-3*a(n-10)+2*a(n-13)+a(n-14) G.f.: -(x^8+x^7-x^6-2*x^4-x^2-x+1)/(x^14+2*x^13-3*x^10-x^8-8*x^7+x^6+3*x^4+2*x-1)
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CROSSREFS
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Cf. A002524-A002529, A072827, A072850-A072856, A079955-A080014.
Sequence in context: A093702 A011756 A050950 this_sequence A091270 A045703 A122025
Adjacent sequences: A079988 A079989 A079990 this_sequence A079992 A079993 A079994
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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 17 2003
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