OFFSET
0,1
LINKS
Colin Barker, Table of n, a(n) for n = 0..900
Tomislav Došlić and Frode Måløy, Chain hexagonal cacti: Matchings and independent sets, Discr. Math., 310 (2010), 1676-1690.
Index entries for linear recurrences with constant coefficients, signature (10, 7).
FORMULA
From Colin Barker, Nov 25 2017: (Start)
a(n) = ((5-4*sqrt(2))^n*(-1+sqrt(2)) + (1+sqrt(2))*(5+4*sqrt(2))^n) / sqrt(2).
a(n) = 10*a(n-1) + 7*a(n-2) for n > 1.
(End)
MATHEMATICA
CoefficientList[Series[(2-2x)/(1-10x-7x^2), {x, 0, 30}], x] (* or *) LinearRecurrence[{10, 7}, {2, 18}, 30] (* Harvey P. Dale, Feb 25 2020 *)
PROG
(PARI) Vec(2*(1 - x) / (1 - 10*x - 7*x^2) + O(x^40)) \\ Colin Barker, Nov 25 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, May 22 2010
STATUS
approved