OFFSET
1,1
COMMENTS
The identity (388962*n^2-1764*n+1)^2-(441*n^2-2*n)*(18522*n-42)^2=1 can be written as A157739(n)^2-A157737(n)*a(n)^2=1. - Vincenzo Librandi, Jan 25 2012
This is the case s=21 of the identity (2*s^4*n^2-4*s^2*n+1)^2-(s^2*n^2-2*n)*(2*s^3*n-2*s)^2=1. - Bruno Berselli, Feb 05 2011
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Index entries for linear recurrences with constant coefficients, signature (2,-1).
FORMULA
G.f.: x*(18480+42*x)/(x-1)^2. - Vincenzo Librandi, Jan 25 2012
a(n) = 2*a(n-1) - a(n-2). - Vincenzo Librandi, Jan 25 2012
MAPLE
MATHEMATICA
LinearRecurrence[{2, -1}, {18480, 37002}, 40] (* Vincenzo Librandi, Jan 25 2012 *)
PROG
(Magma) I:=[18480, 37002]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..40]]; // Vincenzo Librandi, Jan 25 2012
(PARI) for(n=1, 22, print1(18522*n - 42", ")); \\ Vincenzo Librandi, Jan 25 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Mar 05 2009
STATUS
approved