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 | 5 |
| 3 | 16 |
| 4 | 66 |
| 5 | 352 |
| 6 | 2431 |
| 7 | 21760 |
| 8 | 252586 |
| 9 | 3803648 |
| 10 | 74327145 |
| 11 | 1885102080 |
| 12 | 62062015500 |
| 13 | 2652584509440 |
| 14 | 147198472495020 |
| 15 | 10606175914819584 |
| 16 | 992340657705109416 |
| 17 | 120567366227960791040 |
| 18 | 19023173201224270401428 |
| 19 | 3897937005297330777227264 |