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Search: id:A123620
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| A123620 |
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G.f.: (1+x+x^2)/(1-3*x-3*x^2). |
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+0
1
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| 1, 4, 16, 60, 228, 864, 3276, 12420, 47088, 178524, 676836, 2566080, 9728748, 36884484, 139839696, 530172540, 2010036708, 7620627744, 28891993356, 109537863300, 415289569968, 1574482299804, 5969315609316, 22631393727360, 85802128010028, 325300565212164
(list; graph; listen)
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OFFSET
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0,2
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REFERENCES
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A. Burstein and T. Mansour, Words restricted by 3-letter ..., Annals. Combin., 7 (2003), 1-14.
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LINKS
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Index entries for sequences related to linear recurrences with constant coefficients
A. Burstein and T. Mansour, Words restricted by 3-letter ....
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FORMULA
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a(0)=1, a(1)=4, a(2)=16, a(n)=3*a(n-1)+3*a(n-2) for n>2. [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Sep 18 2009]
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CROSSREFS
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Sequence in context: A032106 A047097 A051043 this_sequence A126929 A133161 A103820
Adjacent sequences: A123617 A123618 A123619 this_sequence A123621 A123622 A123623
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Nov 20 2006
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