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 | 3 |
| 2 | 9 |
| 3 | 30 |
| 4 | 120 |
| 5 | 582 |
| 6 | 3354 |
| 7 | 22488 |
| 8 | 172320 |
| 9 | 1487208 |
| 10 | 14284296 |
| 11 | 151179696 |
| 12 | 1748521296 |
| 13 | 21945019392 |
| 14 | 297077918976 |
| 15 | 4315269544704 |
| 16 | 66952906801920 |
| 17 | 1105127533048320 |
| 18 | 19337110495511040 |
| 19 | 357542547031249920 |
| 20 | 6965984564179246080 |
| 21 | 142638952766943744000 |
| 22 | 3062533108375448064000 |