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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 240 |
| 6 | 2160 |
| 7 | 20160 |
| 8 | 201600 |
| 9 | 2177280 |
| 10 | 29030400 |
| 11 | 439084800 |
| 12 | 7185024000 |
| 13 | 124540416000 |
| 14 | 2266635571200 |
| 15 | 44460928512000 |
| 16 | 941525544960000 |
| 17 | 21341245685760000 |
| 18 | 512189896458240000 |