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 | 3 |
| 3 | 21 |
| 4 | 220 |
| 5 | 2846 |
| 6 | 41621 |
| 7 | 670568 |
| 8 | 11570877 |
| 9 | 210605770 |
| 10 | 3998468431 |
| 11 | 78556582448 |
| 12 | 1587757499592 |
| 13 | 32866068149376 |
| 14 | 694307793698105 |
| 15 | 14927522659021682 |
| 16 | 325895131806047690 |
| 17 | 7211436102222542901 |
| 18 | 161493494674514291108 |
| 19 | 3655277488432342084426 |