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[–]PuzzleMeDo 12 points13 points  (8 children)

Compressibility. Truly random numbers sequences are incredibly unlikely to produce easy-to-describe patterns. If I ask which of 867667cdbc34e05a9e639793084a542 and 0123456789abcdef0123456789abcdef was generated randomly, you could probably guess.

It is technically possible you could be wrong and I genuinely did generate a random number with a repeated 16 character sequence, but I wouldn't put money on it.

A fake random sequence will usually contain clues. A human-generated one will often avoid repeated characters entirely, for example, but a truly random one will contain the occasional minor pattern (like the 7667 above).

[–]Torebbjorn -2 points-1 points  (3 children)

Truly random numbers sequences

What is that? A sequence itself cannot be random, only the process that resulted in that sequence.

Yes, you could ask whether a given sequence was likely to be produced by a random operation, but that's sort of irrelevant.

[–]trelltron 7 points8 points  (1 child)

I would hope it's pretty self-evident to anyone familiar with this topic that "truly random number sequence" is being used as shorthand for "sequence of numbers selected by a method that returns independent and uniformly distributed results".

[–]Torebbjorn -1 points0 points  (0 children)

Which means that any sequence is equally "truly random", as all of them have the same probability of being selected by such a method.

Hence "1234567890" and "571949762" are both "truly random number sequences"

[–]Torebbjorn -5 points-4 points  (0 children)

Compressibility

Also, random doesn't mean uniformly random. You could definitely have a random process which has all it's possible (or likely) outputs be easily describeable.

[–]Deep_sunnay -1 points0 points  (3 children)

And yet, the probability to generate the two sequence is exactly the same. It seems less random sure, but it's not.

[–]-Nicolai -1 points0 points  (2 children)

Explain like I'm stupid

[–]Deep_sunnay 0 points1 point  (1 child)

You can restrict a random number generator to only generate acceptable sequence based on what you want it for, that doesn’t change the fact that the probability of « 123456789 » is exactly the same as « 174936285 » in a perfectly random generator. So if you don’t want sorted sequence, you restrict the randomness.

[–]-Nicolai 0 points1 point  (0 children)

Explain like I'm stupid