Hexnet Hexagonal Tag Feed: triangular number A feed of tagged nodes. https://hexnet.org/blog Tetractys <p> The Tetractys is a triangular figure of ten points arranged in four rows, equivalent to the fourth triangular number. It was considered sacred by the ancient Pythagoreans of yore. </p> Sun, 20 Jun 2010 02:14:14 +0000 https://hexnet.org/content/tetractys https://hexnet.org/content/tetractys