316012domain: NAppears in sequencesThe number of rectangles (orthogonal or not) with corners on an n X n grid of points.at n=27A085582L.g.f.: A(x) = log( 1 + Sum_{n>=1} (n-1)!*x^n ) = Sum_{n>=1} a(n)*x^n/n.at n=8A141154The binary expansion of a(n) is the first n terms of 2 - A000002.at n=19A329356