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Search: id:A079977
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| A079977 |
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Fibonacci numbers interspersed with zeros. |
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+0
2
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| 1, 0, 1, 0, 2, 0, 3, 0, 5, 0, 8, 0, 13, 0, 21, 0, 34, 0, 55, 0, 89, 0, 144, 0, 233, 0, 377, 0, 610, 0, 987, 0, 1597, 0, 2584, 0, 4181, 0, 6765, 0, 10946, 0, 17711, 0, 28657, 0, 46368, 0, 75025, 0, 121393, 0, 196418, 0, 317811, 0, 514229, 0, 832040, 0, 1346269
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OFFSET
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0,5
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COMMENT
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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=1, r=3, I={0,2}.
Number of compositions of n into elements of the set {2,4}.
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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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a(n)=A000045(k+1) if n=2k, a(n)=0 otherwise.
Recurrence: a(n) = a(n-2)+a(n-4). G.f.: -1/(x^4+x^2-1).
a(n) = a(n-4) + a(n-2). - Jon Schoenfield (jonscho(AT)hiwaay.net), Aug 07 2006
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CROSSREFS
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Cf. A002524-A002529, A072827, A072850-A072856, A079955-A080014, A000045.
Adjacent sequences: A079974 A079975 A079976 this_sequence A079978 A079979 A079980
Sequence in context: A066682 A049641 A035363 this_sequence A008799 A011013 A138325
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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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EXTENSIONS
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Editorial note: normally the alternate zeros are omitted from sequences like this. This entry is an exception. - njas
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