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729180, 1458180, 2187180, 2916180, 3645180, 4374180, 5103180, 5832180, 6561180, 7290180, 8019180, 8748180, 9477180, 10206180, 10935180, 11664180, 12393180, 13122180, 13851180, 14580180, 15309180, 16038180, 16767180, 17496180
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The identity (32805000n^2+16200*n+1)^2-(2025n^2+n)*(729000n+180)^2=1 can be written as A157081(n)^2-A156856(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. 180*x*(4051-x)/(x-1)^2.
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MATHEMATICA
| LinearRecurrence[{2, -1}, {729180, 1458180}, 40]
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PROG
| (MAGMA) I:=[729180, 1458180]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..30]];
(PARI) a(n)=729000*n+180 \\ Charles R Greathouse IV, Dec 23 2011
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CROSSREFS
| Cf. A156867, A156856, A157081.
Sequence in context: A100383 A204150 A156867 * A107447 A184504 A147707
Adjacent sequences: A156865 A156866 A156867 * A156869 A156870 A156871
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KEYWORD
| nonn,easy
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Feb 17 2009
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