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 | 8 |
| 3 | 120 |
| 4 | 1016 |
| 5 | 8520 |
| 6 | 68552 |
| 7 | 551496 |
| 8 | 4415048 |
| 9 | 35344632 |
| 10 | 282781304 |
| 11 | 2262444024 |
| 12 | 18099745784 |
| 13 | 144799511928 |
| 14 | 1158397641080 |
| 15 | 9267193490808 |
| 16 | 74137560288632 |
| 17 | 593100581182152 |
| 18 | 4744804748330312 |
| 19 | 37958438777603016 |
| 20 | 303667511011784648 |
| 21 | 2429340094421767752 |