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 | 1 |
| 2 | 4 |
| 3 | 42 |
| 4 | 904 |
| 5 | 34070 |
| 6 | 2019888 |
| 7 | 174588120 |
| 8 | 20804747136 |
| 9 | 3276218158560 |
| 10 | 659664288364800 |
| 11 | 165425062846302336 |
| 12 | 50574549124825998336 |
| 13 | 18520126461205806360144 |
| 14 | 8003819275469728355033088 |
| 15 | 4031020344281171589447408000 |
| 16 | 2340375822778055527109749211136 |