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 | 2 |
| 3 | 2 |
| 4 | 8 |
| 5 | 40 |
| 6 | 80 |
| 7 | 560 |
| 8 | 4480 |
| 9 | 4480 |
| 10 | 44800 |
| 11 | 492800 |
| 12 | 1971200 |
| 13 | 25625600 |
| 14 | 358758400 |
| 15 | 1793792000 |
| 16 | 28700672000 |
| 17 | 487911424000 |
| 18 | 975822848000 |
| 19 | 18540634112000 |
| 20 | 370812682240000 |
| 21 | 2595688775680000 |
| 22 | 57105153064960000 |
| 23 | 1313418520494080000 |
| 24 | 10507348163952640000 |