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.
Z + (288*x^2 - 30*x)*_Z^2 + (256*x^3 - 27*x^2)*_Z^4): seq(coeff(series(f, x, 20), x, n), n = 0..19); # _Peter Luschny has authored 0 sequences.