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 | 0 |
| 3 | 3 |
| 4 | -8 |
| 5 | 100 |
| 6 | -834 |
| 7 | 11438 |
| 8 | -159928 |
| 9 | 2762352 |
| 10 | -52322160 |
| 11 | 1124320032 |
| 12 | -26509832040 |
| 13 | 686751503568 |
| 14 | -19306448087640 |
| 15 | 586539826169880 |
| 16 | -19131996548499264 |
| 17 | 667157522614934016 |
| 18 | -24762890955027112128 |
| 19 | 974824890777753840576 |
| 20 | -40566428716555791936000 |