2
$\begingroup$

I saw this symbol: $\underline{\big|6} $ in a question bank for a chapter of permutations and combinations. I have included the question from the book to provide more context: image link.

$\endgroup$
6
  • 1
    $\begingroup$ Unless it's just a typo, I have no idea. $\endgroup$
    – lulu
    Commented Dec 14, 2018 at 19:20
  • 2
    $\begingroup$ The symbol means $6!$ $\endgroup$ Commented Dec 14, 2018 at 19:21
  • 4
    $\begingroup$ That's an old symbol for the factorial of a number. It was mostly phased out by the early 1900s, but you can find it in most 1800s algebra textbooks. $\endgroup$ Commented Dec 14, 2018 at 19:21
  • $\begingroup$ Use of this symbol is referenced in this answer and the comments indicate a usage by Hilbert. $\endgroup$
    – Mason
    Commented Dec 14, 2018 at 19:26
  • 1
    $\begingroup$ @DaveL.Renfro Make an answer out of your comment :) $\endgroup$
    – mrtaurho
    Commented Dec 14, 2018 at 19:28

1 Answer 1

6
$\begingroup$

This an old symbol for the factorial of a number. It was mostly phased out by the early 1900s, but you can find it in most 1800s literature, especially mathematicians in Great Britain. A useful historical survey of various notations for factorial is given in

Florian Cajori, History of symbols for $\underline{n}=$ factorial, Isis 3 #3 (Summer 1921), 414-418.

$\endgroup$

Not the answer you're looking for? Browse other questions tagged .