This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
?(PrimeQ@ GCD[#, n] &)], {n, 84}] (* _Michael De Vlieger's wiki page.
?(PrimeQ@ GCD[#, n] &)], {n, 84}] (* _Michael De Vlieger has authored 0 sequences.