OFFSET
0,3
COMMENTS
In general, Sum_{k=0..floor(n/2)} C(2n-2k,2k)a^k*b^(n-k) has expansion (1-bx-abx^2)/(1-2bx-(2ab-b^2)x^2-2ab^2*x^3+(ab)^2*x^4).
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (2,5,6,-9).
FORMULA
G.f.: (1-x-3x^2)/(1-2x-5x^2-6x^3+9x^4).
a(n) = 2a(n-1)+5a(n-2)+6a(n-3)-9a(n-4).
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Jun 04 2005
STATUS
approved