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 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 54 |
| 4 | 580 |
| 5 | 6873 |
| 6 | 86688 |
| 7 | 1141500 |
| 8 | 15512220 |
| 9 | 215928900 |
| 10 | 3063184410 |
| 11 | 44124882750 |
| 12 | 643692232404 |
| 13 | 9490176205006 |
| 14 | 141184118174640 |
| 15 | 2116751269990968 |
| 16 | 31951313566227228 |
| 17 | 485159929343783532 |
| 18 | 7405637373574690968 |
| 19 | 113572576254948487800 |
| 20 | 1749075343256441443320 |