175539domain: NAppears in sequencesExpansion of 1/((1-x)*(1-3*x)*(1-4*x)*(1-9*x)).at n=5A021379Number of subsets of {1, 2, ..., n} containing n and having <=9 pairwise coprime elements.at n=40A186993Number of quadrilaterals in a triangular matchstick arrangement of side n.at n=27A2041853*n analog to Keith numbers.at n=20A282758