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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 24 |
| 4 | 9216 |
| 5 | 772680 |
| 6 | 20864640 |
| 7 | 281690640 |
| 8 | 2408469504 |
| 9 | 14923820016 |
| 10 | 72840764160 |
| 11 | 295839890280 |
| 12 | 1038542714880 |
| 13 | 3238606068984 |
| 14 | 9155710252416 |
| 15 | 23832538897440 |
| 16 | 57817164625920 |
| 17 | 131989025850720 |
| 18 | 285757100158464 |
| 19 | 590483650831416 |
| 20 | 1170770734955520 |