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 | 2 |
| 2 | 20 |
| 3 | 152 |
| 4 | 1040 |
| 5 | 6752 |
| 6 | 42560 |
| 7 | 263552 |
| 8 | 1614080 |
| 9 | 9815552 |
| 10 | 59417600 |
| 11 | 358602752 |
| 12 | 2160005120 |
| 13 | 12993585152 |
| 14 | 78095728640 |
| 15 | 469111242752 |
| 16 | 2816814940160 |
| 17 | 16909479575552 |
| 18 | 101491237191680 |
| 19 | 609084862103552 |
| 20 | 3655058928435200 |
| 21 | 21932552593866752 |
| 22 | 131604111656222720 |
| 23 | 789659854309425152 |
| 24 | 4738099863344906240 |
| 25 | 28429162130022858752 |