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 | 0 |
| 2 | 2 |
| 3 | 12 |
| 4 | 48 |
| 5 | 600 |
| 6 | 5760 |
| 7 | 65520 |
| 8 | 967680 |
| 9 | 14515200 |
| 10 | 250387200 |
| 11 | 4790016000 |
| 12 | 98195328000 |
| 13 | 2204365363200 |
| 14 | 53178757632000 |
| 15 | 1371750412032000 |
| 16 | 37828404117504000 |
| 17 | 1107254963662848000 |
| 18 | 34316723062702080000 |