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240, 490, 740, 990, 1240, 1490, 1740, 1990, 2240, 2490, 2740, 2990, 3240, 3490, 3740, 3990, 4240, 4490, 4740, 4990, 5240, 5490, 5740, 5990, 6240, 6490, 6740, 6990, 7240, 7490, 7740, 7990, 8240, 8490, 8740, 8990, 9240, 9490, 9740, 9990, 10240, 10490
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| The identity (1250*n^2-100*n+1)^2-(25*n^2-2*n)*(250*n-10)^2=1 can be written as A154374(n)^2-A154376(n)*a(n)^2=1 (see also the second comment in A154374). - Vincenzo Librandi, Jan 30 2012
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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). - Vincenzo Librandi, Jan 30 2012
G.f.: x*(10*x+240)/(x-1)^2. - Vincenzo Librandi, Jan 30 2012
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MATHEMATICA
| LinearRecurrence[{2, -1}, {240, 490}, 50] (* Vincenzo Librandi, Jan 30 2012 *)
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PROG
| (PARI) a(n)=250*n-10 \\ Charles R Greathouse IV, Dec 27 2011
(MAGMA) I:=[240, 490]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]]; // Vincenzo Librandi, Jan 30 2012
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CROSSREFS
| Cf. A154374, A154376.
Sequence in context: A179644 A099833 A179440 * A063372 A070123 A119659
Adjacent sequences: A154375 A154376 A154377 * A154379 A154380 A154381
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KEYWORD
| nonn,easy
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AUTHOR
| Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Jan 08 2009
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