[考古] 阶乘符号

hbghlyj

这本英国旧书把$n+1$的阶乘写成$\enclose{left bottom}{n+1}$ 好像比$(n+1)!$方便一些
在19世纪的英美用过一段时间,后来因排版困难不再使用了:

Wikipedia: Another later notation, in which the argument of the factorial was half-enclosed by the left and bottom sides of a box, was popular for some time in Britain and America but fell out of use, perhaps because it is difficult to typeset.

在History of Symbols for $n$ Factorial查到

The notation $\enclose{left bottom}{n}$ was suggested in 1827 by Thomas Jarrett (1805-1882) who had just graduated from St Catherine's College in Cambridge, England, with the degree of B. A. It occurs in a paper « On Algebraic Notation » that was printed in 1830.

在Thomas Jarrett查到这个符号源自德语:

It contained a suggestion for the notation for a factorial, written $\enclose{left bottom}{n}$ as opposed to $n!$ (a notation of German origin), that had wide currency in the nineteenth century.

对应的MathML为

1. <menclose notation="left bottom">
2.   <mi>n</mi>
3.   <mo>+</mo>
4.   <mn>1</mn>
5. </menclose>

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MathML <menclose>查到madruwb为Arabic factorial symbol (阿语向左书写)
2010年3月 讨论