Keywords: Congruum.svg congruum it is the difference between consecutive values in the arithmetic progression of squares 7<sup>2</sup> 13<sup>2</sup> 17<sup>2</sup> Equivalently the two annuli between the three yellow circles have equal areas Ï times the congruum 2014-12-06 own David Eppstein other versions cc-zero Uploaded with UploadWizard Right triangles |