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 | 0 |
| 3 | 0 |
| 4 | 6 |
| 5 | 30 |
| 6 | 105 |
| 7 | 315 |
| 8 | 3388 |
| 9 | 47628 |
| 10 | 497115 |
| 11 | 4172025 |
| 12 | 37829946 |
| 13 | 491971194 |
| 14 | 7699457857 |
| 15 | 114432747975 |
| 16 | 1602464966040 |
| 17 | 23767387469688 |
| 18 | 408590795439351 |
| 19 | 7756561553900085 |
| 20 | 149537297087139910 |
| 21 | 2889288053301888630 |
| 22 | 58297667473293537597 |