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A145121
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Numbers n such that there exists x in N : (x+19)^3-x^3=n^2.
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1
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361, 108661, 32815261, 9910100161, 2992817433361, 903820954774861, 272950935524574661, 82430278707466772761, 24893671218719440799161, 7517806277774563654573861, 2270352602216699504240506861, 685638968063165475716978498161, 207060698002473756967023265937761
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OFFSET
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1,1
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LINKS
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FORMULA
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a(n+2) = 302*a(n+1)-a(n).
G.f.: -361*x*(x-1) / (x^2-302*x+1). - Colin Barker, Oct 19 2014
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EXAMPLE
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a(1)=361 because 57^3-38^3=361^2.
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MATHEMATICA
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CoefficientList[Series[361 (1 - x)/(x^2 - 302 x + 1), {x, 0, 20}], x] (* Vincenzo Librandi, Oct 19 2014
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PROG
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(PARI) Vec(-361*x*(x-1)/(x^2-302*x+1) + O(x^20)) \\ Colin Barker, Oct 19 2014
(Magma) I:=[361, 108661]; [n le 2 select I[n] else 302*Self(n-1)-Self(n-2): n in [1..15]]; // Vincenzo Librandi, Oct 19 2014
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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