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A120775
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a(n) = 3*a(n-1) + 5*a(n-2) + a(n-3).
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0
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1, 6, 23, 100, 421, 1786, 7563, 32040, 135721, 574926, 2435423, 10316620, 43701901, 185124226, 784198803, 3321919440, 14071876561, 59609425686, 252509579303, 1069647742900, 4531100550901, 19194049946506, 81307300336923
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = 3*a(n-1) + 5*a(n-2) + a(n-3).
G.f. -x*(1+3*x) / ( (1+x)*(x^2+4*x-1) ). a(n) + a(n+1) = A048876(n). - R. J. Mathar, Oct 22 2013
a(n) = (Lucas(3n-1) + (-1)^n)/2. - Greg Dresden, Oct 09 2020
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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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EXTENSIONS
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STATUS
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approved
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