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 | 18 |
| 2 | 220 |
| 3 | 2280 |
| 4 | 21616 |
| 5 | 194208 |
| 6 | 1685440 |
| 7 | 14290560 |
| 8 | 119232256 |
| 9 | 983566848 |
| 10 | 8047836160 |
| 11 | 65462691840 |
| 12 | 530198327296 |
| 13 | 4280634482688 |
| 14 | 34479631482880 |
| 15 | 277245459333120 |
| 16 | 2226418414452736 |
| 17 | 17862092934217728 |
| 18 | 143201285904793600 |
| 19 | 1147437816702566400 |
| 20 | 9190468809917464576 |