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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 6 |
| 5 | 30 |
| 6 | 270 |
| 7 | 1386 |
| 8 | 6048 |
| 9 | 46656 |
| 10 | 387180 |
| 11 | 2469060 |
| 12 | 17204616 |
| 13 | 158065128 |
| 14 | 1903506696 |
| 15 | 18887563800 |
| 16 | 163657221120 |
| 17 | 2095170230016 |
| 18 | 30792968596368 |
| 19 | 346564643468976 |
| 20 | 3905503235814240 |
| 21 | 58609511127871200 |
| 22 | 866032039742528736 |