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 | 8 |
| 3 | 45 |
| 4 | 315 |
| 5 | 2634 |
| 6 | 25518 |
| 7 | 280257 |
| 8 | 3434595 |
| 9 | 46400310 |
| 10 | 684374076 |
| 11 | 10933866027 |
| 12 | 187983528813 |
| 13 | 3458845917990 |
| 14 | 67787903801790 |
| 15 | 1409293876400019 |
| 16 | 30968525550983913 |
| 17 | 717023025711440082 |
| 18 | 17442766619178969600 |
| 19 | 444704318660973471885 |
| 20 | 11855331996299677291131 |