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27, 111, 251, 447, 699, 1007, 1371, 1791, 2267, 2799, 3387, 4031, 4731, 5487, 6299, 7167, 8091, 9071, 10107, 11199, 12347, 13551, 14811, 16127, 17499, 18927, 20411, 21951, 23547, 25199, 26907, 28671, 30491, 32367, 34299, 36287, 38331, 40431
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OFFSET
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1,1
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COMMENTS
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The identity (28*n^2-1)^2-(196*n^2-14)*(2*n)^2 = 1 can be written as a(n)^2 - A158553(n)*A005843(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 (3,-3,1).
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FORMULA
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G.f.: x*(-27-30*x+x^2)/(x-1)^3.
a(n)= 3*a(n-1) -3*a(n-2) +a(n-3).
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MATHEMATICA
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28Range[50]^2-1 (* From Harvey P. Dale, Mar 17 2011 *)
LinearRecurrence[{3, -3, 1}, {27, 111, 251}, 40] (* Vincenzo Librandi, Feb 14 2012 *)
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PROG
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(MAGMA) I:=[27, 111, 251]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+Self(n-3): n in [1..50]]; // Vincenzo Librandi, Feb 14 2012
(PARI) for(n=1, 40, print1(28*n^2-1", ")); \\ Vincenzo Librandi, Feb 14 2012
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CROSSREFS
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Cf. A005843, A158553.
Sequence in context: A193393 A143938 A042428 * A029699 A087795 A036927
Adjacent sequences: A158551 A158552 A158553 * A158555 A158556 A158557
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KEYWORD
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nonn,easy
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AUTHOR
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Vincenzo Librandi, Mar 21 2009
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EXTENSIONS
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Comment rewritten - R. J. Mathar, Oct 16 2009
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STATUS
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approved
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