2710440domain: NAppears in sequencesExpansion of e.g.f.: (1-x)^(-1-x).at n=9A073479Number of nX4 1..4 arrays with all 1s connected, all 2s connected, all 3s connected, all 4s connected, 1 in the upper left corner, 2 in the upper right corner, 3 in the lower left corner, and 4 in the lower right corner.at n=5A164750