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 | 0 |
| 1 | 1 |
| 2 | -1 |
| 3 | 4 |
| 4 | -16 |
| 5 | 91 |
| 6 | -616 |
| 7 | 4894 |
| 8 | -44416 |
| 9 | 453541 |
| 10 | -5145856 |
| 11 | 64222984 |
| 12 | -874402816 |
| 13 | 12897183391 |
| 14 | -204862698496 |
| 15 | 3486535686274 |
| 16 | -63292764553216 |
| 17 | 1220795601029641 |
| 18 | -24931903045697536 |
| 19 | 537463528325234764 |
| 20 | -12196043454064623616 |
| 21 | 290588368323926512291 |
| 22 | -7253387436695186046976 |