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 | 12 |
| 6 | 40 |
| 7 | 180 |
| 8 | 630 |
| 9 | 3360 |
| 10 | 22680 |
| 11 | 113400 |
| 12 | 831600 |
| 13 | 7484400 |
| 14 | 38918880 |
| 15 | 302702400 |
| 16 | 2918916000 |
| 17 | 20432412000 |
| 18 | 205837632000 |
| 19 | 2500927228800 |
| 20 | 21598916976000 |
| 21 | 263986763040000 |
| 22 | 3837961401120000 |
| 23 | 33774060329856000 |
| 24 | 431557437548160000 |
| 25 | 6658314750743040000 |