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 | 2 |
| 4 | 6 |
| 5 | 20 |
| 6 | 80 |
| 7 | 384 |
| 8 | 2016 |
| 9 | 12096 |
| 10 | 82080 |
| 11 | 597888 |
| 12 | 4783104 |
| 13 | 41886720 |
| 14 | 389145600 |
| 15 | 3891456000 |
| 16 | 41803776000 |
| 17 | 472283136000 |
| 18 | 5667397632000 |
| 19 | 72153317376000 |
| 20 | 959814696960000 |
| 21 | 13437405757440000 |
| 22 | 197840194965504000 |
| 23 | 3028176742219776000 |
| 24 | 48450827875516416000 |