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1020, 2020, 3020, 4020, 5020, 6020, 7020, 8020, 9020, 10020, 11020, 12020, 13020, 14020, 15020, 16020, 17020, 18020, 19020, 20020, 21020, 22020, 23020, 24020, 25020, 26020, 27020, 28020, 29020, 30020, 31020, 32020, 33020, 34020, 35020
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The identity (5000n^2+200n+1)^2-(25n^2+n)*(1000n+20)^2=1 can be written as A157511(n)^2-A173089(n)*a(n)^2=1 (see also second part of the comment in A173089). - Vincenzo Librandi, Feb 04 2012
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Vincenzo Librandi, X^2-AY^2=1
Index to sequences with linear recurrences with constant coefficients, signature (2,-1).
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FORMULA
| G.f.: x*(1020-20*x)/(1-x)^2. - Vincenzo Librandi, Feb 04 2012
a(n) = 2*a(n-1)-a(n-2). - Vincenzo Librandi, Feb 04 2012
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MATHEMATICA
| LinearRecurrence[{2, -1}, {1020, 2020}, 50] (* Vincenzo Librandi, Feb 04 2012 *)
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PROG
| MAGMA) I:=[1020, 2020]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]]; // Vincenzo Librandi, Feb 04 2012
(PARI) for(n=1, 40, print1(1000*n + 20", ")); \\ Vincenzo Librandi, Feb 04 2012
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CROSSREFS
| Cf. A157511, A173089.
Sequence in context: A087837 A051982 A104444 * A015160 A102925 A024020
Adjacent sequences: A157507 A157508 A157509 * A157511 A157512 A157513
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KEYWORD
| nonn,easy,changed
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Mar 02 2009
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