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 | 9 |
| 2 | 63 |
| 3 | 315 |
| 4 | 1161 |
| 5 | 8505 |
| 6 | 112455 |
| 7 | 796635 |
| 8 | 2843505 |
| 9 | 57661065 |
| 10 | 1099313775 |
| 11 | 9327901275 |
| 12 | 92211082425 |
| 13 | 1678394943225 |
| 14 | 32985192014775 |
| 15 | 598006256722875 |
| 16 | 4499525524118625 |
| 17 | 75554867738975625 |
| 18 | 4316991655250649375 |