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 | 20 |
| 3 | 504 |
| 4 | 17160 |
| 5 | 742560 |
| 6 | 39070080 |
| 7 | 2422728000 |
| 8 | 173059286400 |
| 9 | 13995229248000 |
| 10 | 1264020397516800 |
| 11 | 126115611484262400 |
| 12 | 13776096431889792000 |
| 13 | 1635195634511530291200 |
| 14 | 209574860127295703040000 |
| 15 | 28844656968251942737920000 |
| 16 | 4243193364951971128258560000 |
| 17 | 664387519844376163893657600000 |