All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Numbers
Reversible Cubes (Posted on 2021-06-29) Difficulty: 4 of 5
Consider positive integers which are perfect cubes, do not end in zero, are not palindromes, and their reverse is also a perfect cube.

Q1: Find the smallest such reversible cube which also contains a string of 4 consecutive zeros.

Q2: What do the following pairs of integers have to do with these reversible cubes, and what pair would come next? (hint: see Conjecture 1)

(11, 13), (19, 25), (35, 49), (37, 41), (39, 57), (43, 53), (67, 97)

Conjectures:

(1) the cube roots of all reversible cubes contain only two unique digits, 'a' and 'b'.

(2) the first digit of all reversible cubes is 'c' and the next non-zero digit is always 'd'.

Bonus Questions related to Conjectures:

What are a and b; and what are c and d?

Can you prove the conjectures to be either true or false? (I have not been able to do so)

If a proof is not possible, can you offer an explanation for this finding? (I cannot)

  Submitted by Larry    
Rating: 5.0000 (1 votes)
Solution: (Hide)
1000033000363001331 which is 1000011^3

It's reverse is:

1331003630003300001 which is 1100001^3

The pairs of integers are what you get if you start with the pairs of reversible cubes, take the cube roots, note that they are all 1's and 0's, pretend that these are binary numbers and convert to base 10.

The next several pairs after (11, 13), (19, 25), (35, 49), (37, 41), (39, 57), (43, 53), (67, 97)

are: (69, 81), (71, 113), (75, 105), (77, 89), (83, 101)

Answers to questions related to conjectures:

a and b are 1 and 0

c is 1, d is 3

I have no explanation or proof.

Another curiosity:

The digits 2, 5, 8 do not appear in the first 24 reversible cubes

See also: https://oeis.org/A035124

The first 24 reversible cubes

[1033364331, 1334633301, 1003303631331, 1331363033001, 1000330036301331, 1003033061330301, 1003333697667631, 1030331603303001, 1030637669664331, 1331036300330001, 1334669667360301, 1367667963333001, 1000033000363001331, 1000303030604030301, 1000333036964367631, 1003036067396364331, 1003306637937633301, 1030304060303030001, 1030334663666631331, 1033367397366033001, 1331003630003300001, 1331366663664330301, 1334636937606303001, 1367634696303330001]

Comments: ( You must be logged in to post comments.)
  Subject Author Date
re: computer explorationMark2021-09-30 05:16:02
re: computer explorationMark2021-09-30 04:44:12
re: computer explorationJason Walter2021-07-16 02:51:25
Some Thoughtscomputer explorationCharlie2021-06-29 11:34:06
A startJer2021-06-29 10:24:55
Please log in:
Login:
Password:
Remember me:
Sign up! | Forgot password


Search:
Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (3)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:
Copyright © 2002 - 2024 by Animus Pactum Consulting. All rights reserved. Privacy Information