Timeline for What is the sum of the reciprocal of all of the factors of a number?
Current License: CC BY-SA 3.0
7 events
| when toggle format | what | by | license | comment | |
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| Feb 9, 2017 at 16:53 | vote | accept | Simply Beautiful Art | ||
| Mar 12, 2016 at 10:40 | comment | added | Jeppe Stig Nielsen | @RaviFernando Yes, usually abundance is the difference $\sigma(n) - 2n$ while abundancy is the ratio $\frac{\sigma(n)}{n} = \sigma_{-1}(n)$. But one may have to repeat that definition to make sure everyone knows. A number whose abundancy is an integer, is called a multiply perfect number. Two or more numbers sharing the same abundancy are called friendly numbers. | |
| Mar 12, 2016 at 2:34 | comment | added | Ravi Fernando | This function is sometimes called the abundancy of a number, since $n$ is abundant if $f(n) > 2$, deficient if $f(n) < 2$, and perfect if $f(n) = 2$. See mathworld.wolfram.com/Abundancy.html. Note that Wikipedia (en.wikipedia.org/wiki/Abundant_number) uses the word "abundance" to mean something related but different, and "abundancy index" for your $f(n)$. | |
| Mar 11, 2016 at 23:53 | history | edited | Simply Beautiful Art | CC BY-SA 3.0 | deleted 4 characters in body |
| Mar 11, 2016 at 23:51 | history | edited | Christopher Carl Heckman | CC BY-SA 3.0 | added 31 characters in body |
| Mar 11, 2016 at 23:50 | comment | added | Simply Beautiful Art | Hm, interesting. Thank you. | |
| Mar 11, 2016 at 23:50 | history | answered | Christopher Carl Heckman | CC BY-SA 3.0 |