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 | 40 |
| 7 | 280 |
| 8 | 2240 |
| 9 | 2240 |
| 10 | 22400 |
| 11 | 246400 |
| 12 | 246400 |
| 13 | 3203200 |
| 14 | 44844800 |
| 15 | 44844800 |
| 16 | 717516800 |
| 17 | 12197785600 |
| 18 | 12197785600 |
| 19 | 231757926400 |
| 20 | 4635158528000 |
| 21 | 4635158528000 |
| 22 | 101973487616000 |
| 23 | 2345390215168000 |
| 24 | 2345390215168000 |
| 25 | 58634755379200000 |
| 26 | 1524503639859200000 |
| 27 | 1524503639859200000 |