Here's a nice challenge that I made up thinking about compressing data one night... Print out a number that you can read within it: The numbers 1 to 20(easier) or 1 to 99(very hard) Rules: →Can be read forward or backwards and use same numbers eg. 123 you can read 1,2,3,11,12,22,21,23,32,33 →Cannot! have any two digit repeats eg. 121 you can read 12 foward and also backwards! exception! any double numbers like 11 22 33 etc. The smaller the answer in digits the better. (easy) Here is the answer I get going from 1 to 20 starting with writing a 0123456789 down. 1520123456789113416718 and again starting with writing 8642013579, 17418642013579112516 Is there a better number out there that is shorter yet? (hard) starting with the number 10 I get: (10 doesn't have to end up at the start) 795875564736032972691715211041361802248243358394450776688990 This is the best attempt so far I've gotten... I see the number 24 repeated right off the bat so this is wrong. This is turning out to be quite interesting and quite a fun challenge. I would love to know if there is only one unique answer when you start by writing the number 10 down. What would happen if you started with the number 61? I would love to see some answers (either right or wrong!).