Harshad (Niven) numbers on Numberphile

[Tom Duff]

Davide Rotondo mentioned the Harshad numbers earlier today. Coincidentally (?) Numberphile had a video about them yesterday.

https://www.youtube.com/watch?v=dgwevhEykWQ

Harshad numbers seem way more interesting than the usual digit-fiddling stuff that pervades recreational mathematics. Several interesting conjectures in the video.

[Max Alekseyev]

Nice video!

I was surprised to see my value of A060159(17) cited there. In fact, just a few days ago I was thinking about starting an HPC project to fill up the gaps in A060159.

Regards,

Max

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[Joshua Searle]

It was mentioned that 432! is the first non-Harshad factorial. I did try searching the OEIS but there does not appear to be a sequence for such numbers - or at least I couldn't find it. I would expect that they would get more common with increasing n.

Joshua.

[Robert Israel]

See  A066419

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[Joshua Searle]

Ah, thanks for that! It is quite hard with only one term to go off if you don't match the right keywords!

As I expected, it does get more common, and quite quickly by the looks of it.

Joshua.