Ciro Santilli @cirosantilli 37

As usual, blame the Russians.

There is a Turing machine that halts for every member of the language with the answer yes, but does not necessarily halt for non-members.

Non-examples: cs.stackexchange.com/questions/52503/non-recursively-enumerable-languages

Determines if an executable is a position independent executable (PIE).

Seems to be informational only, since not used by Linux kernel 5.0 or glibc 2.29.

file 5.36 however does use it to display file type as explained at: stackoverflow.com/questions/34519521/why-does-gcc-create-a-shared-object-instead-of-an-executable-binary-according-to/55704865#55704865

The default feathers-chat app runs on NeDB (local filesystem JSON database).

Ciro Santilli managed to port it to Sequelize for PostgreSQL as shown at: github.com/cirosantilli/feathers-chat/tree/sequelize-pg

4 squares are sufficient by Lagrange's four-square theorem.

3 is not enough by Legendre's three-square theorem.

The subsets reachable with 2 and 3 squares are fully characterized by Legendre's three-square theorem.

Complexity: NP-intermediate as of 2020:

The basis of RSA: RSA. But not proved NP-complete, which leads to: