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 | 4 |
| 3 | -31 |
| 4 | 293 |
| 5 | -3499 |
| 6 | 51284 |
| 7 | -891276 |
| 8 | 17928335 |
| 9 | -409921846 |
| 10 | 10500040633 |
| 11 | -297796771914 |
| 12 | 9262574642871 |
| 13 | -313459274848233 |
| 14 | 11464944476563718 |
| 15 | -450647901022275715 |
| 16 | 18943108018829605740 |
| 17 | -847933752191806388254 |
| 18 | 40266301788890216414608 |
| 19 | -2021846883773977115156632 |