OFFSET
0,2
COMMENTS
This sequence is related to paired pattern P_2 in Section 3.2 in Pan and Remmel's link.
LINKS
Ran Pan, Jeffrey B. Remmel, Paired patterns in lattice paths, arXiv:1601.07988 [math.CO], 2016.
FORMULA
G.f.: (-1 + 3*f(x) - 2*x*(-2 + 5*f(x)+ 6*f(x)*x))/(2*(4*x - 1) (-1 + 4*x*(1 + x))), where f(x) = sqrt(1 - 4*x).
a(n) = binomial(2*n,n) - A268431(n).
CROSSREFS
KEYWORD
nonn
AUTHOR
Ran Pan, Feb 04 2016
STATUS
approved