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 | 1 |
| 2 | 15 |
| 3 | 539 |
| 4 | 28980 |
| 5 | 1295404 |
| 6 | -177715720 |
| 7 | -88870557952 |
| 8 | -11213754156480 |
| 9 | 11072302541223336 |
| 10 | 8352732988619491824 |
| 11 | -1800044600955923261688 |
| 12 | -8483589341410812834791040 |
| 13 | -2945489916041839476122254560 |