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2574, 6968, 11362, 15756, 20150, 24544, 28938, 33332, 37726, 42120, 46514, 50908, 55302, 59696, 64090, 68484, 72878, 77272, 81666, 86060, 90454, 94848, 99242, 103636, 108030, 112424, 116818, 121212, 125606, 130000, 134394, 138788, 143182
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The identity (57122*n^2-47320*n+9801)^2-(169*n^2-140*n+29)*(4394*n-1820)^2=1 can be written as A156721(n)^2-A156639(n)*a(n)^2=1.
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Index to sequences with linear recurrences with constant coefficients, signature (2,-1).
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FORMULA
| a(n) = 2*a(n-1) -a(n-2).
G.f.: x*(2574+1820*x)/(x-1)^2.
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MATHEMATICA
| LinearRecurrence[{2, -1}, {2574, 6968}, 40]
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PROG
| (MAGMA) I:=[2574, 6968]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]];
(PARI) a(n)=4394*n-1820 \\ Charles R Greathouse IV, Dec 23 2011
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CROSSREFS
| Cf. A156639, A156718, A156721.
Sequence in context: A125492 A170794 A068265 * A175016 A031789 A001294
Adjacent sequences: A156624 A156625 A156626 * A156628 A156629 A156630
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KEYWORD
| nonn,easy
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Feb 15 2009
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