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A157862
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a(n) = 1728000*n + 240.
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3
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1728240, 3456240, 5184240, 6912240, 8640240, 10368240, 12096240, 13824240, 15552240, 17280240, 19008240, 20736240, 22464240, 24192240, 25920240, 27648240, 29376240, 31104240, 32832240, 34560240, 36288240, 38016240
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OFFSET
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1,1
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COMMENTS
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The identity (103680000*n^2 + 28800*n + 1)^2 - (3600*n^2 + n)*(1728000*n + 240)^2 = 1 can be written as A157863(n)^2 - A157861(n)*a(n)^2 = 1. - Vincenzo Librandi, Jan 25 2012
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LINKS
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FORMULA
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G.f.: x*(1728240 - 240*x)/(1-x)^2. - Colin Barker, Jan 17 2012
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MATHEMATICA
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LinearRecurrence[{2, -1}, {1728240, 3456240}, 40] (* Vincenzo Librandi, Jan 25 2012 *)
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PROG
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(Magma) I:=[1728240, 3456240]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..30]]; // Vincenzo Librandi, Jan 25 2012
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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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