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A063758
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a(0)=1, a(n) = 2*Fibonacci(n+4) - 6.
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1
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1, 4, 10, 20, 36, 62, 104, 172, 282, 460, 748, 1214, 1968, 3188, 5162, 8356, 13524, 21886, 35416, 57308, 92730, 150044, 242780, 392830, 635616, 1028452, 1664074, 2692532, 4356612, 7049150, 11405768, 18454924, 29860698, 48315628, 78176332, 126491966
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OFFSET
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0,2
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REFERENCES
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P. de la Harpe, Topics in Geometric Group Theory, Univ. Chicago Press, 2000, p. 158.
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LINKS
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FORMULA
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G.f.: (1+2*x+2*x^2+x^3)/((1-x-x^2)*(1-x)).
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MAPLE
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seq(`if`(n=0, 1, 2*combinat[fibonacci](n+4)-6), n=0..35); # Nathaniel Johnston, Jun 28 2011
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MATHEMATICA
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PROG
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(PARI) { for (n=0, 500, if (n, a=2*fibonacci(n+4) - 6, a=1); write("b063758.txt", n, " ", a) ) } \\ Harry J. Smith, Aug 29 2009
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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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