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A196472
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a(1)=1; a(n) = floor((3 + sqrt(21))*a(n-1)/2) for n > 1.
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2
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1, 3, 11, 41, 155, 587, 2225, 8435, 31979, 121241, 459659, 1742699, 6607073, 25049315, 94969163, 360055433, 1365073787, 5175387659, 19621384337, 74390315987, 282035100971, 1069276250873
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OFFSET
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1,2
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COMMENTS
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Contains only odd numbers.
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LINKS
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FORMULA
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G.f.: -x*(-1+ x + x ^2) / ( (x-1)*(3*x^2 + 3*x - 1) ). - R. J. Mathar, Oct 04 2011
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MATHEMATICA
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With[{c=(3+Sqrt[21])/2}, NestList[Floor[c*#]&, 1, 30]] (* Harvey P. Dale, Apr 23 2014 *)
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PROG
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(Magma) I:=[1, 3, 11]; [n le 3 select I[n] else 4*Self(n-1)-3*Self(n-3): n in [1..30]]: // Vincenzo Librandi, Oct 05 2011
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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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