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15, 42, 69, 96, 123, 150, 177, 204, 231, 258, 285, 312, 339, 366, 393, 420, 447, 474, 501, 528, 555, 582, 609, 636, 663, 690, 717, 744, 771, 798, 825, 852, 879, 906, 933, 960, 987, 1014, 1041, 1068, 1095, 1122, 1149, 1176, 1203, 1230, 1257, 1284, 1311, 1338
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| The identity (81n^2+90n+26)^2-(9n^2+10n+3)*(27n+15)^2=1 can be written as A154277(n+1)^2-A154254(n+1)*a(n)^2=1. - Vincenzo Librandi, Feb 03 2012
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..10000
Index to sequences with linear recurrences with constant coefficients, signature (2,-1).
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FORMULA
| G.f.: 3*(5+4*x)/(x-1)^2. - R. J. Mathar, Jan 05 2011
a(n) = 3*A017221(n). - R. J. Mathar, Jan 05 2011
a(n) = 2*a(n-1)-a(n-2). - Vincenzo Librandi, Feb 02 2012
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MATHEMATICA
| Range[15, 7000, 27] (* From Vladimir Joseph Stephan Orlovsky, Jul 13 2011 *)
LinearRecurrence[{2, -1}, {15, 42}, 40] (* Vincenzo Librandi, Feb 02 2012 *)
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PROG
| (PARI) a(n)=27*n+15 \\ Charles R Greathouse IV, Dec 28 2011
(MAGMA) I:=[15, 42]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]]; // Vincenzo Librandi, Feb 02 2012
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CROSSREFS
| Cf. A154254, A154277.
Sequence in context: A024845 A056698 A070007 * A173351 A051867 A008976
Adjacent sequences: A154264 A154265 A154266 * A154268 A154269 A154270
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KEYWORD
| nonn,easy,changed
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Jan 06 2009
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