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 | 2 |
| 5 | 0 |
| 6 | 4 |
| 7 | 0 |
| 8 | 12 |
| 9 | 8 |
| 10 | 12 |
| 11 | 64 |
| 12 | 760 |
| 13 | 2080 |
| 14 | 11524 |
| 15 | 77672 |
| 16 | 454376 |
| 17 | 2972720 |
| 18 | 19274208 |
| 19 | 160500016 |
| 20 | 1150812148 |
| 21 | 9797154696 |
| 22 | 79646705916 |
| 23 | 771589104392 |