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 | 5 |
| 3 | -10 |
| 4 | 30 |
| 5 | -74 |
| 6 | 199 |
| 7 | -515 |
| 8 | 1355 |
| 9 | -3540 |
| 10 | 9276 |
| 11 | -24276 |
| 12 | 63565 |
| 13 | -166405 |
| 14 | 435665 |
| 15 | -1140574 |
| 16 | 2986074 |
| 17 | -7817630 |
| 18 | 20466835 |
| 19 | -53582855 |
| 20 | 140281751 |
| 21 | -367262376 |
| 22 | 961505400 |
| 23 | -2517253800 |
| 24 | 6590256025 |
| 25 | -17253514249 |
| 26 | 45170286749 |
| 27 | -118257345970 |
| 28 | 309601751190 |
| 29 | -810547907570 |