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.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 15 |
| 3 | 4140 |
| 4 | 10480142147 |
| 5 | 128064670049908713818925644 |
| 6 | 172134143357358850934369963665272571125557575184049758045339873395 |