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 | 1 |
| 4 | 0 |
| 5 | -5 |
| 6 | 21 |
| 7 | -59 |
| 8 | 117 |
| 9 | -95 |
| 10 | -484 |
| 11 | 3131 |
| 12 | -11219 |
| 13 | 28216 |
| 14 | -40975 |
| 15 | -49778 |
| 16 | 630853 |
| 17 | -2758309 |
| 18 | 8205948 |
| 19 | -16014181 |
| 20 | 3933569 |
| 21 | 135111669 |
| 22 | -743995720 |
| 23 | 2566032656 |
| 24 | -6105683945 |
| 25 | 6584104436 |
| 26 | 26402611080 |
| 27 | -205994058892 |
| 28 | 825490609412 |
| 29 | -2295266373781 |