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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 3 |
| 5 | 4 |
| 6 | 20 |
| 7 | 216 |
| 8 | 1862 |
| 9 | 13840 |
| 10 | 104904 |
| 11 | 949200 |
| 12 | 10517232 |
| 13 | 130307904 |
| 14 | 1694503824 |
| 15 | 23063845728 |
| 16 | 335427395760 |
| 17 | 5269616092416 |
| 18 | 88835797577472 |
| 19 | 1587229554415104 |
| 20 | 29838489410093184 |
| 21 | 589394278657267200 |
| 22 | 12235109311726689024 |
| 23 | 266570965998899071488 |