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 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 5 |
| 6 | 30 |
| 7 | 42 |
| 8 | 336 |
| 9 | 504 |
| 10 | 5040 |
| 11 | 7920 |
| 12 | 95040 |
| 13 | 154440 |
| 14 | 2162160 |
| 15 | 3603600 |
| 16 | 57657600 |
| 17 | 98017920 |
| 18 | 1764322560 |
| 19 | 3047466240 |
| 20 | 60949324800 |
| 21 | 106661318400 |
| 22 | 2346549004800 |
| 23 | 4151586700800 |
| 24 | 99638080819200 |
| 25 | 177925144320000 |
| 26 | 4626053752320000 |
| 27 | 8326896754176000 |