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 | 0 |
| 1 | 1 |
| 2 | 7 |
| 3 | 66 |
| 4 | 852 |
| 5 | 14020 |
| 6 | 280472 |
| 7 | 6609232 |
| 8 | 179317056 |
| 9 | 5505532992 |
| 10 | 188717617280 |
| 11 | 7143999854464 |
| 12 | 296013377405440 |
| 13 | 13325516967972352 |
| 14 | 647610246703508480 |
| 15 | 33794224057227356160 |
| 16 | 1884620857353101983744 |
| 17 | 111857608180484932648960 |
| 18 | 7040178644779119413723136 |
| 19 | 468349192560992552808841216 |
| 20 | 32836927387372039917034405888 |