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Search: id:A080005
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| A080005 |
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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={-1,1}. |
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+0
1
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| 1, 1, 1, 2, 4, 7, 11, 19, 35, 62, 107, 186, 328, 578, 1012, 1771, 3107, 5455, 9568, 16774, 29417, 51603, 90513, 158741, 278404, 488301, 856448, 1502116, 2634532, 4620700, 8104269, 14214069, 24929981, 43724610, 76688540, 134503903, 235906039
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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) = a(n-1)+a(n-2)+a(n-4)+a(n-5)-2*a(n-6)+a(n-8)-a(n-10) G.f.: -(x^5+x^2-1)/(x^10-x^8+2*x^6-x^5-x^4-x^2-x+1)
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CROSSREFS
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Cf. A002524-A002529, A072827, A072850-A072856, A079955-A080014.
Sequence in context: A007864 A118647 A000802 this_sequence A151992 A024501 A160393
Adjacent sequences: A080002 A080003 A080004 this_sequence A080006 A080007 A080008
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KEYWORD
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nonn
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AUTHOR
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Vladimir Baltic (baltic(AT)matf.bg.ac.yu), Feb 10 2003
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