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A154277
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81n^2 - 72n + 17.
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4
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17, 26, 197, 530, 1025, 1682, 2501, 3482, 4625, 5930, 7397, 9026, 10817, 12770, 14885, 17162, 19601, 22202, 24965, 27890, 30977, 34226, 37637, 41210, 44945, 48842, 52901, 57122, 61505, 66050, 70757, 75626, 80657, 85850, 91205, 96722
(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 a(n+1)^2-A154254(n+1)*A154267(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 (3,-3,1).
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FORMULA
| G.f.: (-17+25*x-170*x^2)/(x-1)^3. - Vincenzo Librandi, Feb 02 2012
a(n) = 3*a(n-1) -3*a(n-2) +a(n-3). - Vincenzo Librandi, Feb 02 2012
a(n) = A017221(n-1)^2+1 with A017221(-1)=-4. - Bruno Berselli, Feb 02 2012
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MATHEMATICA
| LinearRecurrence[{3, -3, 1}, {26, 197, 530}, 40] (* Vincenzo Librandi, Feb 02 2012 *)
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PROG
| (MAGMA) I:=[26, 197, 530]; [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 02 2012
(PARI) for(n=0, 22, print1(81*n^2 - 72*n + 17", ")); \\ Vincenzo Librandi, Feb 02 2012
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CROSSREFS
| Cf. A154254, A154267.
Sequence in context: A031204 A085051 A171954 * A140150 A166658 A033702
Adjacent sequences: A154274 A154275 A154276 * A154278 A154279 A154280
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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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EXTENSIONS
| 92205 replaced by 91205 - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 07 2009
Edited by Charles R Greathouse IV (charles.greathouse(AT)case.edu), Aug 09 2010
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