While re-reading [Tower of Babylon] I recalled a story, somewhat reminiscent of its ending trick, which I read as a teenager and impressed me a lot: "He Who Shrank" by Henry Hassel. Its main character is damned to shrink forever, regressing thorough levels of universes, each an atom of the previous one, and at a moment he reaches ours again. The story is collected in "Before the Golden Age" (edited by Isaac Asimov in 1974, and easily available in the second hand market). It also impressed Asimov himself, who refers to it as a source of inspiration for his favorite story , "The Last Question" (not to confuse with "The Last Answer", one of the entries of your list). By the way, while checking the Internet to get more information about the story I was surprised to discover a web on recursive SF (http://www.nesfa.org/Recursion/index.htm). Maybe it is of interest to you.