Ciro Santilli @cirosantilli 37

en.wikipedia.org/w/index.php?title=Farey_sequence&oldid=1223364653#Sequence_length_and_index_of_a_fractionwhere $\Phi (n)$ is the totient summatory function.

Company founded by Marc Verdiell in his garage, and later acquired by Intel which was going on a optoelectronics buying spree. The division was later sold off in 2023 of course during more difficult times: www.theregister.com/2023/10/31/intel_silicon_photonics_jabil/

On Crunchbase: www.crunchbase.com/organization/lightlogic

It's hard to understand exactly what the company did by Googling it nowadays. Sad and usual fate. Presumably something related to transceiver for fiber-optic communication. Only the patents remain: patents.google.com/?assignee=lightlogic&oq=lightlogic to tell its story to the brave.

www.quora.com/Is-MIT-the-only-place-where-homework-is-called-problem-sets
Terminology by location:
Places that say "problem set":Places that say "problem sheet":Places that say "example sheet":

Ciro Santilli's take on it: Section "Give answers".

A "reduced fraction" is a fraction that has the smallest possible integer numerator and denominator for its value.

For example:is not a reduced fraction, because there is another fraction equal to it but with smaller numerator and denominator:

TODO is it or is not:

mathoverflow.net/questions/11540/what-are-the-most-attractive-turing-undecidable-problems-in-mathematics/11557#11557 contains a good overview of the decidability status of variants over rings other than the integers.

www.jstor.org/stable/1970438 says for prime modulo there is an algorithm.

Question for non-prime modulo: math.stackexchange.com/questions/4944623/are-diophantine-equations-decidable-in-modular-arithmetic