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Search: id:A002524
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| A002524 |
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Number of permutations of length n within distance 2.
(Formerly M1600 N0626)
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69
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| 1, 1, 2, 6, 14, 31, 73, 172, 400, 932, 2177, 5081, 11854, 27662, 64554, 150639, 351521, 820296, 1914208, 4466904, 10423761, 24324417, 56762346, 132458006, 309097942, 721296815, 1683185225, 3927803988
(list; graph; listen)
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OFFSET
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0,3
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REFERENCES
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S. Plouffe, Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques Conjectures}, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.
R. Lagrange, Quelques re'sultats dans la me'trique des permutations, Annales Scientifiques de l'\'{E}cole Normale Sup\'{e}rieure, Paris, 79 (1962), 199-241.
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.
R. P. Stanley, Enumerative Combinatorics I, Example 4.7.16, p. 253.
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LINKS
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S. Plouffe, Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques Conjectures}, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.
S. Plouffe, 1031 Generating Functions and Conjectures, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.
R. Lagrange, Quelques re'sultats dans la me'trique des permutations, Annales Scientifiques de l'\'{E}cole Normale Sup\'{e}rieure, Paris, 79 (1962), 199-241.
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FORMULA
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G.f.: (1+2x^2-x^4)/(1-2x-2x^3+x^5) - Colin Mallows (colinm(AT)research.avayalabs.com), Aug 15 2002
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MAPLE
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A002524:=-(-1+z)/(1-2*z-2*z**3+z**5); [Conjectured by S. Plouffe in his 1992 dissertation.]
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CROSSREFS
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Adjacent sequences: A002521 A002522 A002523 this_sequence A002525 A002526 A002527
Sequence in context: A122958 A122959 A059076 this_sequence A055292 A035592 A096238
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KEYWORD
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nonn,easy
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AUTHOR
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njas
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