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 | 0 |
| 3 | 0 |
| 4 | 8 |
| 5 | 0 |
| 6 | 0 |
| 7 | 52 |
| 8 | 396 |
| 9 | 560 |
| 10 | 3048 |
| 11 | 10672 |
| 12 | 57248 |
| 13 | 128864 |
| 14 | 646272 |
| 15 | 1838784 |
| 16 | 8636880 |
| 17 | 23400992 |
| 18 | 105865688 |
| 19 | 305753680 |
| 20 | 1322849752 |
| 21 | 3862974304 |
| 22 | 16225820000 |
| 23 | 48744080192 |
| 24 | 198673312880 |
| 25 | 607041217056 |
| 26 | 2417584484232 |
| 27 | 7519864632928 |
| 28 | 29320809649000 |
| 29 | 92507134938336 |