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 | 2 |
| 2 | 0 |
| 3 | 24 |
| 4 | 144 |
| 5 | 960 |
| 6 | 4608 |
| 7 | 74048 |
| 8 | 859952 |
| 9 | 9568800 |
| 10 | 109975680 |
| 11 | 1647979872 |
| 12 | 23917274304 |
| 13 | 358378620704 |
| 14 | 5528847787008 |
| 15 | 94307761212304 |
| 16 | 1632598198916544 |
| 17 | 29205907283227776 |
| 18 | 538335591996965760 |
| 19 | 10388234139989630128 |
| 20 | 205386383159397554688 |
| 21 | 4173254005731822569088 |