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 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 60 |
| 6 | 270 |
| 7 | 1890 |
| 8 | 14280 |
| 9 | 128520 |
| 10 | 1096200 |
| 11 | 12058200 |
| 12 | 139043520 |
| 13 | 1807565760 |
| 14 | 22642139520 |
| 15 | 339632092800 |
| 16 | 5237183952000 |
| 17 | 89032127184000 |
| 18 | 1475427973219200 |
| 19 | 28033131491164800 |
| 20 | 543494606861606400 |
| 21 | 11413386744093734400 |
| 22 | 235075995738558374400 |
| 23 | 5406747901986842611200 |
| 24 | 126214560713084056012800 |