OFFSET
1,1
COMMENTS
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Vincenzo Librandi, X^2-AY^2=1, Math Forum, 2007. [Wayback Machine link]
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
G.f.: 23*x*(-22-25*x+x^2)/(x-1)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3).
From Amiram Eldar, Mar 16 2023: (Start)
Sum_{n>=1} 1/a(n) = (1 - cot(Pi/sqrt(23))*Pi/sqrt(23))/46.
Sum_{n>=1} (-1)^(n+1)/a(n) = (cosec(Pi/sqrt(23))*Pi/sqrt(23) - 1)/46. (End)
MAPLE
MATHEMATICA
a[n_] := 529*n^2 - 23; Array[a, 50] (* Amiram Eldar, Mar 16 2023 *)
PROG
(PARI) for(n=1, 40, print1(529*n^2 - 23", ")); \\ Vincenzo Librandi, Feb 17 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Mar 23 2009
EXTENSIONS
Comment rephrased and redundant formula replaced by R. J. Mathar, Oct 19 2009
STATUS
approved