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) |
|---|---|
| 4 | 0 |
| 5 | 1 |
| 6 | 214 |
| 7 | 21225 |
| 8 | 1688424 |
| 9 | 125055400 |
| 10 | 9178531200 |
| 11 | 687848686448 |
| 12 | 53435249786880 |
| 13 | 4336107249936384 |
| 14 | 368887991492608000 |
| 15 | 32948013484980000000 |
| 16 | 3090086319932923969536 |
| 17 | 304136142049322287011840 |
| 18 | 31382704663810285705887744 |
| 19 | 3390841628447041935421747200 |
| 20 | 383124440688361472000000000000 |