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 (3,-3,1).
FORMULA
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).
G.f.: x*(-12481*x^2 + 27362*x - 15137)/(x-1)^3. [corrected by Georg Fischer, May 11 2019]
MATHEMATICA
LinearRecurrence[{3, -3, 1}, {15137, 18049, 21217}, 50]
PROG
(Magma) I:=[15137, 18049, 21217]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..50]];
(PARI) a(n) = 128*n^2 + 2528*n + 12481.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Mar 01 2009
EXTENSIONS
Corrected by Charles R Greathouse IV, Jul 29 2010
STATUS
approved