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 | 90 |
| 4 | 660 |
| 5 | 3846 |
| 6 | 24326 |
| 7 | 148146 |
| 8 | 850920 |
| 9 | 4788114 |
| 10 | 26548704 |
| 11 | 144707622 |
| 12 | 778116870 |
| 13 | 4140736398 |
| 14 | 21836757474 |
| 15 | 114262071558 |
| 16 | 593931441790 |
| 17 | 3069689137294 |
| 18 | 15786994900896 |
| 19 | 80840741811238 |
| 20 | 412406022128206 |
| 21 | 2096937750144962 |
| 22 | 10631278302356284 |
| 23 | 53761972675284874 |