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 | 1 |
| 2 | 8 |
| 3 | 50 |
| 4 | 288 |
| 5 | 1604 |
| 6 | 8800 |
| 7 | 47944 |
| 8 | 260352 |
| 9 | 1411600 |
| 10 | 7647872 |
| 11 | 41420576 |
| 12 | 224294400 |
| 13 | 1214467136 |
| 14 | 6575615488 |
| 15 | 35602384000 |
| 16 | 192760455168 |
| 17 | 1043650265344 |
| 18 | 5650555750400 |
| 19 | 30593342288384 |
| 20 | 165638957801472 |
| 21 | 896804870374400 |