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A187917
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a(n) = (1/4)*(5*(n-1)*P(n)+n*P(n-1)) where P() are the Pell numbers A000129.
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0
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0, 3, 14, 50, 160, 481, 1390, 3908, 10768, 29215, 78302, 207798, 546960, 1429821, 3715870, 9608200, 24734816, 63429563, 162099950, 412993210, 1049319872, 2659463705, 6725142286, 16971369036, 42748016880, 107489296599, 269850534206, 676460107070, 1693434156592, 4233924978805
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OFFSET
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1,2
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REFERENCES
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R. P. Grimaldi, Ternary strings with no consecutive 0's and no consecutive 1's, Congressus Numerantium, 205 (2011), 129-149. (The sequence desc_n.)
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LINKS
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FORMULA
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G.f.: x^2*(2*x+3) / (x^2+2*x-1)^2. - Colin Barker, Jul 25 2013
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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