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727, 2912, 6555, 11656, 18215, 26232, 35707, 46640, 59031, 72880, 88187, 104952, 123175, 142856, 163995, 186592, 210647, 236160, 263131, 291560, 321447, 352792, 385595, 419856, 455575, 492752, 531387, 571480, 613031, 656040, 700507, 746432
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OFFSET
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1,1
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COMMENTS
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The identity (729*n-1)^2-(729*n^2-2*n)*(27)^2=1 can be written as A158395(n)^2-a(n)*(27)^2=1.
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LINKS
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FORMULA
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a(n) = 3*a(n-1) -3*a(n-2) +a(n-3).
G.f.: x*(-727-731*x)/(x-1)^3.
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MATHEMATICA
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LinearRecurrence[{3, -3, 1}, {727, 2912, 6555}, 50]
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PROG
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(Magma) I:=[727, 2912, 6555]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..50]];
(PARI) a(n) = 729*n^2 - 2*n.
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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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