OFFSET
1,1
COMMENTS
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Vincenzo Librandi, X^2-AY^2=1
Index entries for linear recurrences with constant coefficients, signature (2,-1).
FORMULA
a(n) = 2*a(n-1) - a(n-2).
G.f.: x*(218295+313146*x)/(x-1)^2.
E.g.f.: 81*((6561*x - 3866)*exp(x) + 3866). - G. C. Greubel, Feb 04 2018
MAPLE
MATHEMATICA
LinearRecurrence[{2, -1}, {218295, 749736}, 40]
Table[531441*n-313146, {n, 1, 30}] (* G. C. Greubel, Feb 04 2018 *)
PROG
(Magma) I:=[218295, 749736]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..50]];
(PARI) a(n) = 531441*n - 313146.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Feb 28 2009
STATUS
approved