OFFSET
0,4
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (0,1,9).
FORMULA
a(n) = a(n-2) + 9*a(n-3).
a(n) = Sum_{k=0..floor(n/2)} binomial(floor((n-k)/2), k)*9^k.
MATHEMATICA
CoefficientList[Series[(1+x)/(1-x^2-9x^3), {x, 0, 30}], x] (* or *) LinearRecurrence[{0, 1, 9}, {1, 1, 1}, 30] (* Harvey P. Dale, Mar 12 2015 *)
PROG
(PARI) x='x+O('x^50); Vec((1+x)/(1-x^2-9*x^3)) \\ G. C. Greubel, Apr 30 2017
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Jul 20 2004
STATUS
approved