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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 8 |
| 5 | 30 |
| 6 | 144 |
| 7 | 840 |
| 8 | 5760 |
| 9 | 45360 |
| 10 | 403200 |
| 11 | 3991680 |
| 12 | 43545600 |
| 13 | 518918400 |
| 14 | 6706022400 |
| 15 | 93405312000 |
| 16 | 1394852659200 |
| 17 | 22230464256000 |
| 18 | 376610217984000 |
| 19 | 6758061133824000 |
| 20 | 128047474114560000 |
| 21 | 2554547108585472000 |
| 22 | 53523844179886080000 |
| 23 | 1175091669949317120000 |