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 | 9 |
| 4 | 32 |
| 5 | -285 |
| 6 | -1236 |
| 7 | 18725 |
| 8 | 86176 |
| 9 | -2087001 |
| 10 | -9204580 |
| 11 | 351964569 |
| 12 | 1336442304 |
| 13 | -83422970917 |
| 14 | -231889447076 |
| 15 | 26389118293005 |
| 16 | 35917342192064 |
| 17 | -10722110983670193 |
| 18 | 5028963509133756 |
| 19 | 5432569724760331841 |
| 20 | -14852185163192897120 |
| 21 | -3352369390318855889661 |