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 | 2 |
| 3 | 9 |
| 4 | 52 |
| 5 | 445 |
| 6 | 5166 |
| 7 | 75019 |
| 8 | 1300776 |
| 9 | 26167257 |
| 10 | 598577770 |
| 11 | 15337224991 |
| 12 | 435020120316 |
| 13 | 13529095809541 |
| 14 | 457727913937854 |
| 15 | 16736043791509995 |
| 16 | 657590281425958096 |
| 17 | 27631245762003186865 |
| 18 | 1236355641557737359570 |
| 19 | 58689534518861119967287 |