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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 2 |
| 6 | 10 |
| 7 | 20 |
| 8 | 70 |
| 9 | 560 |
| 10 | 1680 |
| 11 | 2800 |
| 12 | 30800 |
| 13 | 369600 |
| 14 | 800800 |
| 15 | 11211200 |
| 16 | 168168000 |
| 17 | 448448000 |
| 18 | 7623616000 |
| 19 | 137225088000 |
| 20 | 434546112000 |
| 21 | 8690922240000 |
| 22 | 182509367040000 |
| 23 | 669201012480000 |
| 24 | 15391623287040000 |
| 25 | 369398958888960000 |