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 | 1 |
| 4 | 3 |
| 5 | 6 |
| 6 | 40 |
| 7 | 150 |
| 8 | 2100 |
| 9 | 14700 |
| 10 | 423360 |
| 11 | 5556600 |
| 12 | 325987200 |
| 13 | 8068183200 |
| 14 | 958961203200 |
| 15 | 44996257706400 |
| 16 | 10799101849536000 |
| 17 | 965169727802280000 |
| 18 | 466713183932835840000 |
| 19 | 79775138681769651120000 |