This Lesson (Find a sequence of transformations of a given number to get a desired number) was created by by ikleyn(53419)  : View Source, ShowAbout ikleyn:
Find a sequence of transformations of a given number to get a desired number
Problem 1Starting with a positive integer, apply the following operations any number of times
and in any order to produce a list of numbers:
(1) double the current term, or
(2) delete the last digit of the current term.
An example of such a list is 231, 23, 46, 92, 9, 18.
Find a list which starts with 51 and ends in 129.
Solution
I solved this problem with the help of Artificial Intelligence.
I asked Google AI OVERVIEW:
Is it true that for every k-digit positive integer n,
there is a power of 2 whose first k digits coincide with the number n.
Below is the Google AI Overview answer.
The statement is true. [1]
For every k-digit positive integer n, there is a power of two whose first digits coincide with the number n.
This is a consequence of the fact that log_{10}(2) is an irrational number, which implies that the fractional parts
of m*log_{10}(2) are uniformly distributed in the interval [0, 1) (by the Kronecker's Approximation Theorem). [1, 2, 3]
Understanding the condition
For a positive integer P to be the leading digits of a power of two, say 2^m, it must satisfy the inequality:
P times 10^d <= 2^m < (P+1) times 10^d
for some integer d >= 0. This means 2^m has the same leading digits as P, followed by d more digits.
Answer:
The statement is true because any finite sequence of digits can be the leading digits of a power of two.
This relies on the irrationality of log_{10}(2) and the uniform distribution of the fractional parts of its multiples. [1, 5]
References
[1] https://www.quora.com/Prove-that-for-any-natural-number-n-there-esists-a-power-of-2-lets-say-2-k-such-that-2-k-in-its-decimal-expression-is-1-followed-by-n-zeros-and-eventually-other-digits-For-example-for-n-2-2-196-works-How-to-prove-it
[2] https://www.antonellaperucca.net/didactics/Powers-of-2.pdf
[3] https://math.stackexchange.com/questions/1370645/using-kroneckers-theorem-can-we-prove-theres-some-power-of-two-yielding-a-numb
[4] https://math.stackexchange.com/questions/328655/proving-prime-p-divides-binompk-for-k-in-1-ldots-p-1
[5] https://www.reddit.com/r/askmath/comments/18o86pr/is_it_true_that_for_any_positive_integer_n_there/
The link to this Google AI response is
https://www.google.com/search?q=Is+this+statement+true%3F+For+every+k-digit+positive+integer+n%2C+there+is+a+power+of+two+whose+first+n+digits+coincide+with+the+number+n.&rlz=1C1CHBF_enUS1071US1071&oq=Is+this+statement+true%3F+For+every+k-digit+positive+integer+n%2C+there+is+a+power+of+two++whose+first+n+digits+coincide+with+the+number+n.&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQIRiPAjIHCAIQIRiPAjIHCAMQIRiPAtIBCTE3OTZqMGoxNagCCLACAfEFNet2ZYDKsLI&sourceid=chrome&ie=UTF-8
of Dec.4, 2025.
Then I asked Google AI another question:
Find the degree of number 2 which starts 129.
Google AI answered: the degree is 110, and it is first degree of 2 with this property.
Then I checked using MS Excel in my computer
= 1.29807E+33.
Now I can present the desired sequence of operations
51 -> 102 -> 10 -> 1 -> 2 -> 4 -> 8 -> 16 -> 32 -> 64 -> 128 -> . . . . -> = 1.29807E+33,
which is a 34-digit integer number 1298074214633706907132624082305024, whose three starting/leading digits are 129.
Notice that I do not state that this sequence is the shortest possible.
I only state that this explicit sequence produces a desired number.
Thus, the problem is solved and the desired sequence of operations is presented explicitly.
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Yes, in my solution I used help from Google AI Overview - I explicitly referred to it,
so it is not stealing - it is normal work in contemporary environment. Thanks to Google AI for help ( ! )
And it suggests some art asking right questions and interpreting the AI answers properly,
as well as organizing pieces and thoughts into a logically coherent text,
which opens new knowledge and provides new material for teaching and learning.
My other additional lessons on Miscellaneous word problems (section 3) in this site are
- More complicated problems on finding number of elements in finite subsets
- Solving problems by the Backward method
- Minimax linear problems to solve MENTALLY based on common sense
- Solving linear optimization problems without LP-method by reduction to linear function
- Solving one special linear minimax problem in 100-D space by the Linear Programming method
- Miscellaneous logical problems
- Math Olympiad level problem on divisibility numbers
- Upper class entertainment Math problems for all ages
- OVERVIEW of my additional lessons on Miscellaneous word problems, section 3
Use this file/link ALGEBRA-I - YOUR ONLINE TEXTBOOK to navigate over all topics and lessons of the online textbook ALGEBRA-I.
Use this file/link ALGEBRA-II - YOUR ONLINE TEXTBOOK to navigate over all topics and lessons of the online textbook ALGEBRA-II.
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