OFFSET
0,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..100
Index entries for linear recurrences with constant coefficients, signature (0,38,0,-1).
FORMULA
G.f.: (1 + x)*(9 + 10*x - x^2) / (1 - 38*x^2 + x^4). [Bruno Berselli, Oct 30 2013]
a(n) = (2+(-1)^n)*((3-sqrt(10))^(n+1)+(3+sqrt(10))^(n+1))/2. [Bruno Berselli, Oct 30 2013]
MATHEMATICA
Numerator[Convergents[Sqrt[90], 30]] (* Vincenzo Librandi, Oct 29 2013 *)
Table[(2 + (-1)^n) ((3 - Sqrt[10])^(n + 1) + (3 + Sqrt[10])^(n + 1))/2, {n, 0, 30}] (* Bruno Berselli, Oct 30 2013 *)
LinearRecurrence[{0, 38, 0, -1}, {9, 19, 351, 721}, 30] (* Harvey P. Dale, May 12 2018 *)
CROSSREFS
KEYWORD
nonn,cofr,frac,easy
AUTHOR
STATUS
approved