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A006137
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1 + n/2 + 9*n^2/2.
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3
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1, 6, 20, 43, 75, 116, 166, 225, 293, 370, 456, 551, 655, 768, 890, 1021, 1161, 1310, 1468, 1635, 1811, 1996, 2190, 2393, 2605, 2826, 3056, 3295, 3543, 3800, 4066, 4341, 4625, 4918, 5220, 5531, 5851, 6180
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refs;
listen;
history;
text;
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OFFSET
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0,2
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LINKS
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Harvey P. Dale, Table of n, a(n) for n = 0..1000
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FORMULA
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a(n)=3*a(n-1)-3*a(n-2)+a(n-3), with a(0)=1, a(1)=6 and a(2)=20. [From Paolo P. Lava, Jul 17 2009]
a(n)=a(n-1)+9*n-4 (with a(0)=1) [From Vincenzo Librandi, Nov 18 2010]
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MATHEMATICA
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s = 1; lst = {s}; Do[s += n + 4; AppendTo[lst, s], {n, 1, 350, 9}]; lst [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 11 2009]
Table[1+n/2+9 n^2/2, {n, 0, 40}] (* or *) LinearRecurrence[{3, -3, 1}, {1, 6, 20}, 40] (* Harvey P. Dale, Oct 05 2012 *)
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CROSSREFS
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Sequence in context: A094274 A094279 A093913 * A225269 A048969 A005564
Adjacent sequences: A006134 A006135 A006136 * A006138 A006139 A006140
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane.
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STATUS
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approved
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