is beehaw related to lemmy?

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Joined 1 year ago
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Cake day: June 8th, 2023

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  • Indeed, an integer is divisible by 3 if and only if the sum of its digits is divisible by 3.

    For proof, take the polynomial representation of an integer n = a_0 * 10^k + a_1 * 10^{k-1} + … + a_k * 1. Note that 10 mod 3 = 1, which means that 10^i mod 3 = (10 mod 3)^i = 1. This makes all powers of 10 = 1 and you’re left with n = a_0 + a_1 + … + a_k. Thus, n is divisible by 3 iff a_0 + a_1 + … + a_k is. Also note that iff answers your question then; all multiples of 3 have to, by definition, have digits whose sum is a multiple of 3

















  • Holy shit dude, that was actually very helpful! I’ll need a few more go-throughs to fully grasp every piece here, but thanks a ton for writing it so precisely.

    Based on this though, is there no way to have port-forwarding except setting it up explicitly in my router? I ask this because 1) in my personal setup, I’ll be switching between wifi and mobile data quite often, and 2) I may end up on an institutional wifi after some time, in which case I won’t have access to the router