OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (3,0,1).
FORMULA
G.f.: (1-x)^2/(1-3*x-x^3).
a(n) = Sum_{k=0..floor(n/2)} binomial(n+k,3*k) * 3^k.
MAPLE
a:= proc(n) option remember;
`if`(n<2, 1, 3*a(n-1)+a(n-3))
end:
seq(a(n), n=0..30); # Alois P. Heinz, May 25 2022
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Paul Barry, Aug 30 2004
STATUS
approved