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 | 720 |
| 3 | 17640 |
| 4 | 726570 |
| 5 | 17236728 |
| 6 | 223847280 |
| 7 | 1928224440 |
| 8 | 12500672580 |
| 9 | 65073916440 |
| 10 | 284229347328 |
| 11 | 1080456070680 |
| 12 | 3650778821970 |
| 13 | 11191823745120 |
| 14 | 31612753519200 |
| 15 | 83017908015624 |
| 16 | 204808695842610 |
| 17 | 479043914067360 |
| 18 | 1065816689968080 |
| 19 | 2271147404056200 |