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 | -2 |
| 3 | 15 |
| 4 | -200 |
| 5 | 3920 |
| 6 | -102924 |
| 7 | 3424946 |
| 8 | -139217280 |
| 9 | 6733296720 |
| 10 | -379945682400 |
| 11 | 24634909864752 |
| 12 | -1813131434947392 |
| 13 | 149981854962931680 |
| 14 | -13828816882622028000 |
| 15 | 1411324560147609680400 |