Rafael S.T. Vieira - MATLAB Cody - MATLAB Central

Rafael S.T. Vieira

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Rafael S.T. Vieira submitted a Comment to Problem 54345. Fill a rectangle with 1x1 and 2x2 tiles

It seems easy, then hard, then easy again.

on 27 Nov 2022

Rafael S.T. Vieira submitted a Comment to Problem 53990. Classify product/digit-sum sequences

Tip FYI: If the sum of the digits of a number is divisible by 3, then the number is also divisible by 3, and the same rule exists for 9. All numbers have similar laws, it seems. A number divisible by 5 ends with 0 or 5, and so on...

on 26 Nov 2022

Rafael S.T. Vieira submitted a Comment to Problem 53990. Classify product/digit-sum sequences

I didn't find a key, but a predominance between the five lists: 9 is the most powerful. 4 or 5 tests are enough, but some have made matrices with more than 25 possible combinations.

on 26 Nov 2022

Rafael S.T. Vieira submitted a Comment to Problem 53880. List the vile numbers

A more accurate description of the problem would be binary numbers that start with an even number of zeros but not necessarily those that have or end with an even number of zeros.

on 26 Nov 2022

Rafael S.T. Vieira submitted a Comment to Problem 51950. Find the smallest integer m such that n divides m!

May I suggest using Kempner(Kempner(Kempner(123456787654321))+10) as a test against lookup tables?

on 25 Nov 2022

Rafael S.T. Vieira submitted a Comment to Problem 51950. Find the smallest integer m such that n divides m!

Unfortunately, it does not stop lookup tables since 134 factors to 2 and 67, which means it obtains the same result as a lookup table. Kempner(Kempner(Kempner(1535238))) will do 134 -> 67 -> 67 and a lookup table 67->67->67.

on 25 Nov 2022

Rafael S.T. Vieira submitted a Comment to Solution 6611739

Nice solution using the Euler's totient function. I've tried it too, but I couldn't figure out a friendly algorithm like this. I've resorted to my probability knowledge :)

on 25 Nov 2022

Rafael S.T. Vieira submitted a Comment to Problem 52729. Easy Sequences 21: Combinatorial Summations

S(20) = 177547, you're welcome.

on 24 Nov 2022

Rafael S.T. Vieira submitted a Comment to Problem 52729. Easy Sequences 21: Combinatorial Summations

Tip: This problem is not solved using combinations or factorials.

on 24 Nov 2022
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