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 | 6 |
| 3 | 24 |
| 4 | 160 |
| 5 | 1100 |
| 6 | 9168 |
| 7 | 84336 |
| 8 | 868544 |
| 9 | 9806688 |
| 10 | 120754080 |
| 11 | 1608251040 |
| 12 | 23036978688 |
| 13 | 353070167424 |
| 14 | 5764504370688 |
| 15 | 99875064159360 |
| 16 | 1830107743518720 |
| 17 | 35360088597841920 |
| 18 | 718450398365755392 |
| 19 | 15313427783968370688 |
| 20 | 341652563064038062080 |
| 21 | 7962756873168407869440 |