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Cake day: August 15th, 2023

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  • Never realized there are so many rules for divisibility. This post fits in this category:

    Forming an alternating sum of blocks of three from right to left gives a multiple of 7

    299,999 would be 999 - 299 = 700 which is divisible by 7. And if we simply swap grouped digits to 999,299, it is also divisible by 7 since 299 - 999 = -700.

    And as for 13:

    Form the alternating sum of blocks of three from right to left. The result must be divisible by 13

    So we have 999 - 999 + 299 = 299.

    You can continue with other rules so we can then take this

    Add 4 times the last digit to the rest. The result must be divisible by 13.

    So for 299 it’s 29 + 9 * 4 = 65 which divides by 13. Pretty cool.







  • Interesting observation, but maybe it is just a coincidence since I am not aware these numbers appearing anywhere? Found this reddit thread that talks about same thing.

    Here’s an interview with controller′s designer that explains the meaning behind symbols. I think number theory is just a coincidence since I think it would be mentioned in this interview as well.

    Other game companies at the time assigned alphabet letters or colors to the buttons. We wanted something simple to remember, which is why we went with icons or symbols, and I came up with the triangle-circle-X-square combination immediately afterward. I gave each symbol a meaning and a color. The triangle refers to viewpoint; I had it represent one’s head or direction and made it green. Square refers to a piece of paper; I had it represent menus or documents and made it pink. The circle and X represent ‘yes’ or ‘no’ decision-making and I made them red and blue respectively. People thought those colors were mixed up, and I had to reinforce to management that that’s what I wanted.