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*(-2649601-131529598*x-73180801*x^2)/(x-1)^3.
MATHEMATICA
LinearRecurrence[{3, -3, 1}, {2649601, 139478401, 483667201}, 40]
Table[103680000n^2-174211200n+73180801, {n, 20}] (* Harvey P. Dale, Feb 19 2024 *)
PROG
(Magma) I:=[2649601, 139478401, 483667201]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..40]];
(PARI) a(n) = 103680000*n^2 - 174211200*n + 73180801.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Mar 07 2009
STATUS
approved