OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: -(-2+(-3*w^2-6*w+1)^(1/2))/(1+w)^2.
MATHEMATICA
T[0, 0] = 1; T[n_, 0] = 0; T[n_, k_] /; 0 <= k <= n := T[n, k] = T[n, k - 1] + T[n - 1, k - 1] + T[n - 1, k] + T[n - 2, k - 1]; T[_, _] = 0; Table[T[n, n], {n, 0, 25}] (* G. C. Greubel, Jan 04 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jan 24 2001
STATUS
approved