OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (3,-1,1).
FORMULA
G.f. : (1-x)^2/(1-3*x+x^2-x^3).
a(n) = Sum_{k=0..floor(n/2)} binomial(n+k, 3*k) * 2^k.
MATHEMATICA
CoefficientList[Series[(1 - x)^2/(1 - 3 x + x^2 - x^3), {x, 0, 50}], x] (* G. C. Greubel, Mar 03 2017 *)
PROG
(PARI) x='x+O(x^50); Vec((1-x)^2/(1-3*x+x^2-x^3)) \\ G. C. Greubel, Mar 03 2017
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Aug 30 2004
STATUS
approved