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 | 3 |
| 2 | 15 |
| 3 | 90 |
| 4 | 810 |
| 5 | 10530 |
| 6 | 210600 |
| 7 | 6528600 |
| 8 | 319901400 |
| 9 | 24952309200 |
| 10 | 3119038650000 |
| 11 | 626926768650000 |
| 12 | 203124273042600000 |
| 13 | 106233994801279800000 |
| 14 | 89767725607081431000000 |
| 15 | 122622713179273234746000000 |
| 16 | 270873573413014575553914000000 |