101824domain: NAppears in sequencesNumber of line segments connecting exactly 3 points in an n X n grid of points.at n=33A177719Expansion of e.g.f. csch(x)*(1 - sqrt(1 - 4*sinh(x)))/2.at n=6A295254a(n) = (1/2) * Sum_{k=0..floor(n/3)} 2^(n-2*k) * binomial(2*k+2,2*n-6*k+1).at n=18A387556