OFFSET
0,2
COMMENTS
Row sums of A109221.
The Kn4 sums, see A180662, of triangle A065941 equal the terms of this sequence a(n) while the Kn4 sums of triangle A194005 equal a(n+1)-1. - Johannes W. Meijer, Aug 14 2011
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,2,0,-1).
FORMULA
G.f.: (1 + x - x^2 - x^3)/(1 - x - 2x^2 + x^4);
a(n) = a(n-1) + 2a(n-2) - a(n-4);
a(n) = Sum_{k=0..n} binomial(floor((2n-k)/2)+n-k, 2n-2k).
MAPLE
A109222 := proc(n): add(binomial(floor((2*n-k)/2)+n-k, 2*n-2*k), k=0..n) end: seq(A109222(n), n=0..33); # Johannes W. Meijer, Aug 14 2011
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Jun 22 2005
STATUS
approved