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 | 1 |
| 4 | 12 |
| 5 | 120 |
| 6 | 1140 |
| 7 | 10815 |
| 8 | 104496 |
| 9 | 1037484 |
| 10 | 10627560 |
| 11 | 112508550 |
| 12 | 1231481460 |
| 13 | 13933510734 |
| 14 | 162864103584 |
| 15 | 1965078765195 |
| 16 | 24453461392080 |
| 17 | 313549334233440 |
| 18 | 4138796594051568 |
| 19 | 56188737057169593 |
| 20 | 783876449182595400 |