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A124011
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Add three, add six, add nine, ....
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2
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5, 8, 14, 23, 35, 50, 68, 89, 113, 140, 170, 203, 239, 278, 320, 365, 413, 464, 518, 575, 635, 698, 764, 833, 905, 980, 1058, 1139, 1223, 1310, 1400, 1493, 1589, 1688, 1790, 1895, 2003, 2114, 2228, 2345, 2465, 2588, 2714, 2843, 2975, 3110, 3248, 3389, 3533
(list;
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refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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Found on a quiz.
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LINKS
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FORMULA
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G.f.: x*(5 - 7*x + 5*x^2)/(1-x)^3. - Colin Barker, Jan 14 2012
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MATHEMATICA
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PROG
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(Magma) I:=[5, 8, 14]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..50]]; // Vincenzo Librandi, Feb 15 2012
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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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Ruben Fritzon (ruben.fritzon(AT)edu.ovanaker.se), Dec 11 2006
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EXTENSIONS
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More terms from Graham Roy (groy(AT)ashland.edu), Dec 14 2006
Additional comments from Christopher N. Swanson (cswanson(AT)ashland.edu), R. J. Mathar, Dec 14 2006
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STATUS
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approved
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