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Search: id:A123871
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| A123871 |
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G.f.: (1+x+x^2)/(1-4*x-4*x^2). |
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+0
1
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| 1, 5, 25, 120, 580, 2800, 13520, 65280, 315200, 1521920, 7348480, 35481600, 171320320, 827207680, 3994112000, 19285278720, 93117562880, 449611366400, 2170915717120, 10482108334080, 50612096204800, 244376818155520, 1179955657441280, 5697329902387200
(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)=5, a(2)=25, a(n)=4*a(n-1)+4*a(n-2) for n>2. [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Sep 19 2009]
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CROSSREFS
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Sequence in context: A110212 A089927 A068539 this_sequence A078717 A086093 A171279
Adjacent sequences: A123868 A123869 A123870 this_sequence A123872 A123873 A123874
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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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