I am being haunted by a fractal. In a recent column [see "Sierpinski's Ubiquitous Gasket," August 1999] I described several occurrences of the fractal known as Sierpinski's gasket, which can be obtained from a triangle by successively deleting an inverted triangle half its size. Ever since, readers have been alerting me to new sightings of this versatile figure. Its latest incarnation is in the field of mathematical logic. Patrick Grim and Paul St. Denis of the State University of New York at Stony Brook sent me a paper entitled "Fractal Images of Formal Systems" (Journal of Philosophical Logic, Vol. 26, No. 2, pages 181-222; 1997).
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机译：我被一个分形困扰着。在最近的专栏文章中（见“ Sierpinski的无处不在的垫圈”，1999年8月），我描述了多次出现的被称为Sierpinski垫圈的分形，可以从三角形中通过连续删除一半大小的倒三角形来获得。从那以后，读者一直在提醒我这个多功能的人物的新发现。它的最新化身是数学逻辑领域。纽约州立大学石溪分校的帕特里克·格里姆（Patrick Grim）和保罗·圣丹尼斯（Paul St. Denis）给我发送了一篇论文，题目为“形式系统的分形图像”（《哲学逻辑杂志》，第26卷，第2期，第181-222页； 1997年） 。
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