OFFSET
0,2
COMMENTS
Row sums of A108756.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,2,0,-1).
FORMULA
G.f.: (1 + x - x^2)/(1 - x - 2*x^2 + x^4).
a(n) = a(n - 1) + 2*a(n - 2) - a(n - 4) for n >= 4.
a(n) = Sum_{0 <= k <= n} binomial(floor((n + k + 1)/2) + k, floor((n + k)/2) - k).
MATHEMATICA
LinearRecurrence[{1, 2, 0, -1}, {1, 2, 3, 7}, 40] (* Harvey P. Dale, Feb 21 2016 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Jun 22 2005
STATUS
approved