[Intermernet]

On a slight tangent, I recently read a paper on an interesting relationship between Collatz path length and Mersenne primes.

"Our main finding to report is the fact that a path length of a Mersenne prime is approximately proportional to its index for large n, namely, D(Mn) ≈ 13.45n."

Paper is at https://arxiv.org/pdf/1104.2804.pdf . WARNING: PDF.

[jamescostian]

I'm curious, why do people on HN warn about PDFs? The worst things I can imagine happening with PDFs are (1) you don't have any software that can read it (probably like .2% of HNers?) and (2) it could potentially have some malware (but the same could be said of a website)

[geofft]

Before the advent of built-in PDF readers in browsers, it would often either trigger a download or launch an external program, which are kind of rude behaviors to spring on someone without notice. I still have this habit (though I'll just mention "(PDF)" in a parenthetical), and I'll certainly warn about autoplaying audio or an excessive amount of ads even if I expect a good fraction of readers to have browser configs/extensions to deal with those.

[hermitdev]

Adobe is not known for their security. PDF is also known to allow remote execution via PDF. Default reader on most systems being Adobe's reader, yeah, I'd avoid it. I know this is shifting as browsers incorporate readers, but the format is tarnished.

[pronoiac]

The mobile experience for PDFs is awful.

[anoncake]

The mobile experience for HTML/JS/CSS is awful too.

[evanb]

You can de-PDF anything on the arXiv by chopping off the .pdf suffix and changing the /pdf/ to /abs/.

For example, https://arxiv.org/abs/1104.2804

[Intermernet]

Thanks! I love learning little tips like that.