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 | 0 |
| 2 | 2 |
| 3 | 12 |
| 4 | 80 |
| 5 | 720 |
| 6 | 9152 |
| 7 | 165312 |
| 8 | 4244480 |
| 9 | 154732800 |
| 10 | 8005686272 |
| 11 | 587435092992 |
| 12 | 61116916981760 |
| 13 | 9011561121239040 |
| 14 | 1882834327457349632 |
| 15 | 557257804202631217152 |
| 16 | 233610656002563147038720 |
| 17 | 138681207656726645785559040 |
| 18 | 116575238610106596799428165632 |