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72, 315, 720, 1287, 2016, 2907, 3960, 5175, 6552, 8091, 9792, 11655, 13680, 15867, 18216, 20727, 23400, 26235, 29232, 32391, 35712, 39195, 42840, 46647, 50616, 54747, 59040, 63495, 68112, 72891, 77832, 82935, 88200, 93627, 99216, 104967
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The identity (18*n^2-1)^2-(81*n^2-9)*(2*n)^2=1 can be written as A157910(n)^2-a(n)*A005843(n)^2=1. - Vincenzo Librandi, Feb 08 2012
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Vincenzo Librandi, X^2-AY^2=1
Index to sequences with linear recurrences with constant coefficients, signature (3,-3,1).
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FORMULA
| G.f.: -9*x*(8 + 11*x - x^2)/(x - 1)^3. - Vincenzo Librandi, Feb 08 2012
a(n) = 3*a(n-1) -3*a(n-2) +a(n-3). - Vincenzo Librandi, Feb 08 2012
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MATHEMATICA
| LinearRecurrence[{3, -3, 1}, {72, 315, 720}, 50] (* Vincenzo Librandi, Feb 08 2012 *)
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PROG
| (MAGMA) I:=[72, 315, 720]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..40]]; // Vincenzo Librandi, Feb 08 2012
(PARI) for(n=1, 40, print1(81*n^2 - 9", ")); \\ Vincenzo Librandi, Feb 08 2012
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CROSSREFS
| Cf. A005843, A157910.
Sequence in context: A004007 A173546 A205627 * A107314 A090788 A192792
Adjacent sequences: A157906 A157907 A157908 * A157910 A157911 A157912
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KEYWORD
| nonn,easy,changed
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 09 2009
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