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A156774
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6561n^2 - 3564n + 485.
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3
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485, 3482, 19601, 48842, 91205, 146690, 215297, 297026, 391877, 499850, 620945, 755162, 902501, 1062962, 1236545, 1423250, 1623077, 1836026, 2062097, 2301290, 2553605, 2819042, 3097601, 3389282, 3694085, 4012010, 4343057, 4687226
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OFFSET
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0,1
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COMMENTS
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The identity (6561*n^2-3564*n+485)^2-(81*n^2-44*n+6)*(729*n-198)^2=1 can be written as a(n)^2-A156676(n)* A156772(n)^2=1 for n>0.
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 0..10000
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
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FORMULA
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a(n) = 3*a(n-1) -3*a(n-2) +a(n-3).
G.f.: (-485-2027*x-10610*x^2)/(x-1)^3.
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MATHEMATICA
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LinearRecurrence[{3, -3, 1}, {485, 3482, 19601}, 40]
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PROG
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(MAGMA) I:=[485, 3482, 19601]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..40]];
(PARI) a(n)= 6561*n^2-3564*n+485 \\ Charles R Greathouse IV, Dec 23 2011
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CROSSREFS
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Cf. A156676, A156772.
Sequence in context: A160090 A158326 A031722 * A031632 A097767 A031520
Adjacent sequences: A156771 A156772 A156773 * A156775 A156776 A156777
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KEYWORD
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nonn,easy
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AUTHOR
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Vincenzo Librandi, Feb 15 2009
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EXTENSIONS
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Edited by Charles R Greathouse IV, Jul 25 2010
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STATUS
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approved
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