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 | 1 |
| 4 | 6 |
| 5 | 15 |
| 6 | 120 |
| 7 | 933 |
| 8 | 13303 |
| 9 | 252207 |
| 10 | 6450828 |
| 11 | 205475039 |
| 12 | 7936493756 |
| 13 | 363639228194 |
| 14 | 19476976825809 |
| 15 | 1205115679461426 |
| 16 | 85288127619421544 |
| 17 | 6845235025444882069 |
| 18 | 618411485467843477405 |
| 19 | 62471139399366989007575 |
| 20 | 7014991719815977343879171 |