When bored in class, I used to do a variant on this. However, to make it more complicated, I would add the date and use a 24 hour clock. So, it would be 4161351 right now. I had rules around it and could give up if there were no prime factors < 20. In that case, I would draw a line and reverse the order. If there were still no low prime factors, I would draw a double line and swap pairs of digits. This would allow another single line swap. If there was an odd number of digits > 3, then multiple double line / single line reorderings could occur. If out of options, I would draw a triple line and subtract the current number from 10*9 (regular expression). For instance, 799 would be subtracted from 1009. I couldn't use 999 since that could reduce the number of digits and I wanted a simple way of subtracting to guarantee things would start moving. The resulting number is divisible by 2 and has a 50% chance of being divisible by 3. Note that single and double lines do not change whether a number is divisible by 3 and single lines by 11. Here's what it would look like using 4161351 (mentioned above). Notations are for the reader, I never wrote them in school:
![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
![[identity profile]](https://www.dreamwidth.org/img/silk/identity/openid.png){kind=small}
Geek alert!
Date: 2007-04-16 06:13 pm (UTC)4161351
1387117 (divided by 3)
-------
7117831
1016833 (/7)
-------
3386101
=======
3368011
-------
1108633
-------
=======
8891376
4445688 (/2)
2222844
1111422
555711
185237 (/3)
14249
-----
94241
13463 (/7)
-----
36431
2143 (/17)
----
3412
1706 (/2)
853
---
358 (/2)
179
---
971
===
791
103 (/7)
---
301
43 (/7)
--
34
17 (/2)
1 (/17)
Re: Geek alert!
Date: 2007-04-16 08:23 pm (UTC)I need a "geek" icon. :-)
Re: Geek alert!
Date: 2007-04-16 08:35 pm (UTC)