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 | 0 |
| 2 | 720 |
| 3 | 13440 |
| 4 | 97200 |
| 5 | 455040 |
| 6 | 1714320 |
| 7 | 4821120 |
| 8 | 12380400 |
| 9 | 29043840 |
| 10 | 58980960 |
| 11 | 114076800 |
| 12 | 219310320 |
| 13 | 367338240 |
| 14 | 621878400 |
| 15 | 1037727360 |
| 16 | 1583679600 |
| 17 | 2401816320 |
| 18 | 3747180240 |
| 19 | 5232470400 |
| 20 | 7551983520 |
| 21 | 10938261120 |
| 22 | 14715224640 |
| 23 | 19930775040 |
| 24 | 28073386800 |
| 25 | 35727920640 |