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 | 7 |
| 3 | 54 |
| 4 | 346 |
| 5 | 3732 |
| 6 | 50928 |
| 7 | 636288 |
| 8 | 10421856 |
| 9 | 204446592 |
| 10 | 3783985632 |
| 11 | 84204904320 |
| 12 | 2154137877504 |
| 13 | 52813565568000 |
| 14 | 1488803964595200 |
| 15 | 46983956781312000 |
| 16 | 1434084567201792000 |
| 17 | 48976637440702464000 |
| 18 | 1838658764187353088000 |
| 19 | 67159997418955456512000 |