Nicolas Destainville R. Mosseri F. Bailly A formula for the number of tilings of an octagon by rhombi. 71-81 2004 319 Theor. Comput. Sci. 1-3 http://dx.doi.org/10.1016/j.tcs.2004.02.025 db/journals/tcs/tcs319.html#DestainvilleMB04