To turn a paper sheet into a doughnutlike shape, you need to fold it into at least 16 triangles It’s possible to make a torus by folding a paper sheet just 24 times. The torus has a hole running through the center of it (shown in a computer-generated video). Richard Evan Schwartz Folding a flat piece of paper into a torus — a shape with a hole in the middle — demands origami skill. That’s something mathematician Richard Evan Schwartz lacks. Yet he answered a lingering mathematical question about the process. His work — performed mainly on a computer rather than with paper — reveals the smallest number of folds needed to make a paper torus. The paper must have at least 24 folds , forming 16 triangles that meet at eight points, or vertices, Schwartz reports in the May 26 Proceedings of the National Academy of Sciences . To make a torus from a piece of paper, you can roll it into a tube and bend the tube to connect its two ends, making a doughnut.…