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Search: id:A053599
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| A053599 |
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Number of nonempty subsequences {s(k)} of 1...n such that the difference sequence is palindromic. |
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1
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| 1, 3, 7, 13, 23, 37, 59, 89, 135, 197, 291, 417, 607, 861, 1243, 1753, 2519, 3541, 5075, 7121, 10191, 14285, 20427, 28617, 40903, 57285, 81859, 114625, 163775, 229309, 327611, 458681, 655287, 917429, 1310643, 1834929, 2621359, 3669933, 5242795
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(1)=1, a(2)=3 and, for n>2, a(n)=2a(n-2)+2n-1.
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EXAMPLE
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For n=4 the 13 sequences are 1,2,3,4,12,13,14,23,24,34,123,234,1234.
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CROSSREFS
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The first differences of A053599 gives A027383, the second differences give A016116.
Sequence in context: A131205 A058682 A081995 this_sequence A136851 A122886 A078447
Adjacent sequences: A053596 A053597 A053598 this_sequence A053600 A053601 A053602
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KEYWORD
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nonn
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AUTHOR
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John W. Layman (layman(AT)math.vt.edu), Jan 19 2000
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EXTENSIONS
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Corrected by T. D. Noe (noe(AT)sspectra.com), Nov 08 2006
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