Aha! Thanks. This is a perfect demonstration of the fundamental problem for search-engine users: of course there would be a "jargon term" that designates exactly the particular concept you have in mind -- but when you don't know that term, searches based on various descriptions of (circumlocutions about) the concept tend to have very low precision (and recall success for such queries can be no better than a crap-shoot). There's no substitute for relevant experience... | [reply] |
FYI, I couldn't remember the term so I went to [mathworld://Permutation.html] (Permutation.html). At the bottom are links to "Complete Permutation" and to "Derangement" (clicking the first simply gives a page that points to the second). I've used similar methods to find technical terms for mathematical concepts before; mathematical concepts often have names that are not distinctive so searching for them even when you know them can be problematic. The high degree of cross-linking at MathWorld is one of my favorite features of the site.
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