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122, 243, 364, 485, 606, 727, 848, 969, 1090, 1211, 1332, 1453, 1574, 1695, 1816, 1937, 2058, 2179, 2300, 2421, 2542, 2663, 2784, 2905, 3026, 3147, 3268, 3389, 3510, 3631, 3752, 3873, 3994, 4115, 4236, 4357, 4478, 4599, 4720, 4841, 4962, 5083, 5204
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The identity (121*n+1)^2-(121*n^2+2*n)*(11)^2=1 can be written as a(n)^2-A181679(n)*(11)^2=1.
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Vincenzo Librandi, X^2-AY^2=1
E. J. Barbeau, Polynomial Excursions, Chapter 10: Diophantine equations (2010), pages 84-85 (row 15 in the first table at p. 85, case d(t) = t*(11^2*t+2)).
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*(122-x)/(1-x)^2.
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MATHEMATICA
| LinearRecurrence[{2, -1}, {122, 243}, 50]
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PROG
| (MAGMA) I:=[122, 243]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]];
(PARI) a(n) = 121*n + 1.
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CROSSREFS
| Cf. A181679.
Sequence in context: A207147 A105983 A099154 * A004925 A070955 A195856
Adjacent sequences: A158128 A158129 A158130 * A158132 A158133 A158134
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KEYWORD
| nonn,easy
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 13 2009
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