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 | 1 |
| 3 | -5 |
| 4 | 14 |
| 5 | -40 |
| 6 | 122 |
| 7 | -404 |
| 8 | 1362 |
| 9 | -4608 |
| 10 | 15881 |
| 11 | -55709 |
| 12 | 197402 |
| 13 | -705114 |
| 14 | 2539282 |
| 15 | -9210196 |
| 16 | 33605471 |
| 17 | -123262137 |
| 18 | 454268676 |
| 19 | -1681305246 |
| 20 | 6246544735 |
| 21 | -23288217459 |
| 22 | 87096982499 |
| 23 | -326680267261 |
| 24 | 1228547420236 |
| 25 | -4631474743422 |
| 26 | 17499462106763 |
| 27 | -66257720483935 |
| 28 | 251356773101419 |