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 | 0 |
| 4 | 6 |
| 5 | 30 |
| 6 | 90 |
| 7 | 210 |
| 8 | 1680 |
| 9 | 12096 |
| 10 | 114660 |
| 11 | 833580 |
| 12 | 5928120 |
| 13 | 38112360 |
| 14 | 259194936 |
| 15 | 1739195640 |
| 16 | 17043237120 |
| 17 | 167089937280 |
| 18 | 1837707369840 |
| 19 | 18342985021776 |
| 20 | 181206905922720 |
| 21 | 1673742164139360 |
| 22 | 16992525855006240 |