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728820, 1457820, 2186820, 2915820, 3644820, 4373820, 5102820, 5831820, 6560820, 7289820, 8018820, 8747820, 9476820, 10205820, 10934820, 11663820, 12392820, 13121820, 13850820, 14579820, 15308820, 16037820, 16766820, 17495820
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The identity(32805000*n^2-16200*n+1)^2-(2025*n^2-n)* (729000*n-180)^2=1 can be written as A157080(n)^2-A156855(n)*a(n)^2=1.
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LINKS
| 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
| a(n) = 2*a(n-1) - a(n-2).
G.f.: x*(728820+180*x)/(x-1)^2.
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MATHEMATICA
| LinearRecurrence[{2, -1}, {728820, 1457820}, 40]
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PROG
| (MAGMA) I:=[728820, 1457820]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..40]];
(PARI) a(n)=729000*n-180 \\ Charles R Greathouse IV, Dec 23 2011
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CROSSREFS
| Cf. A156855, A156868, A157080.
Sequence in context: A153581 A100383 A204150 * A156868 A107447 A184504
Adjacent sequences: A156864 A156865 A156866 * A156868 A156869 A156870
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KEYWORD
| nonn,easy
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Feb 17 2009
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