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 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 0 |
| 9 | 0 |
| 10 | 362880 |
| 11 | 39916800 |
| 12 | 2874009600 |
| 13 | 175394419200 |
| 14 | 9967384627200 |
| 15 | 551675124000000 |
| 16 | 30471021291110400 |
| 17 | 1703458301210265600 |
| 18 | 97213825272736972800 |
| 19 | 5693251850259515942400 |
| 20 | 343266731083210449715200 |
| 21 | 21349233350716392722764800 |