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728, 1457, 2186, 2915, 3644, 4373, 5102, 5831, 6560, 7289, 8018, 8747, 9476, 10205, 10934, 11663, 12392, 13121, 13850, 14579, 15308, 16037, 16766, 17495, 18224, 18953, 19682, 20411, 21140, 21869, 22598, 23327, 24056, 24785, 25514, 26243
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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 a(n)^2-A158394(n)*(27)^2=1.
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LINKS
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FORMULA
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a(n) = 2*a(n-1)-a(n-2).
G.f.: x*(728+x)/(1-x)^2.
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MATHEMATICA
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LinearRecurrence[{2, -1}, {728, 1457}, 50]
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PROG
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(Magma) I:=[728, 1457]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]];
(PARI) a(n) = 729*n - 1.
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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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