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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 60 |
| 7 | 640 |
| 8 | 5040 |
| 9 | 39424 |
| 10 | 315840 |
| 11 | 2572800 |
| 12 | 22730400 |
| 13 | 207820800 |
| 14 | 1979577600 |
| 15 | 20119756800 |
| 16 | 180756576000 |
| 17 | 1740900761600 |
| 18 | 17732095180800 |
| 19 | 197872975872000 |
| 20 | 2123068147200000 |
| 21 | 24858537099264000 |
| 22 | 303091124244480000 |
| 23 | 4076808466857984000 |