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A156866
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729000n - 116820.
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3
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612180, 1341180, 2070180, 2799180, 3528180, 4257180, 4986180, 5715180, 6444180, 7173180, 7902180, 8631180, 9360180, 10089180, 10818180, 11547180, 12276180, 13005180, 13734180, 14463180, 15192180, 15921180, 16650180, 17379180
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OFFSET
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1,1
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COMMENTS
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The identity (32805000*n^2-10513800*n+842401)^2-(2025*n^2-3401*n+1428)*(729000*n-116820)^2=1 can be written as A157079(n)^2-A156854(n)*a(n)^2=1.
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Index to sequences with linear recurrences with constant coefficients, signature (2,-1).
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FORMULA
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a(n) = 2*a(n-1) - a(n-2).
G.f. 180*x*(3401+649*x)/(x-1)^2.
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MATHEMATICA
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LinearRecurrence[{2, -1}, {612180, 1341180}, 40]
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PROG
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(MAGMA) I:=[612180, 1341180]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..40]];
(PARI) a(n)=729000*n-116820 \\ Charles R Greathouse IV, Dec 23 2011
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CROSSREFS
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Cf. A156854, A156865, A157079.
Sequence in context: A205429 A195281 A180106 * A206510 A172635 A172707
Adjacent sequences: A156863 A156864 A156865 * A156867 A156868 A156869
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KEYWORD
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nonn,easy
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AUTHOR
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Vincenzo Librandi, Feb 17 2009
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STATUS
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approved
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