OFFSET
1,2
COMMENTS
This equation is used for worked examples in the Robertson link.
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
John P. Robertson, Solving the generalized Pell equation x^2 - Dy^2 = N
Index entries for linear recurrences with constant coefficients, signature (0,0,0,11,0,0,0,-1).
FORMULA
G.f.: x*(x+1)*(x^6+2*x^5+4*x^4+7*x^3+4*x^2+2*x+1) / ((x^4-3*x^2-1)*(x^4+3*x^2-1)).
a(n) = 11*a(n-4)-a(n-8).
MATHEMATICA
LinearRecurrence[{0, 0, 0, 11, 0, 0, 0, -1}, {1, 3, 6, 11, 22, 39, 69, 122}, 50] (* Harvey P. Dale, Jul 07 2022 *)
PROG
(PARI) Vec(x*(x+1)*(x^6+2*x^5+4*x^4+7*x^3+4*x^2+2*x+1)/((x^4-3*x^2-1)*(x^4+3*x^2-1)) + O(x^100))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Aug 16 2013
STATUS
approved