130768domain: NAppears in sequencesNumber of convex quadrilaterals on an n X n grid (or geoboard).at n=6A189413E.g.f. A(x) satisfies: A( sqrt( A(x^2*exp(-2*x)) ) ) = x, where A(x) = Sum_{n>=1} a(n)*x^n/(n-1)!.at n=7A274276Triangle read by rows: T(n, k) = 2^k * hypergeom([-n, -k], [], 1/2).at n=34A375854