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 | 2 |
| 4 | 5 |
| 5 | 13 |
| 6 | 35 |
| 7 | 96 |
| 8 | 264 |
| 9 | 720 |
| 10 | 1925 |
| 11 | 4966 |
| 12 | 12038 |
| 13 | 25907 |
| 14 | 41310 |
| 15 | -5168 |
| 16 | -468996 |
| 17 | -2982240 |
| 18 | -14350320 |
| 19 | -61334790 |
| 20 | -244951840 |
| 21 | -934684465 |
| 22 | -3447083370 |
| 23 | -12365767620 |
| 24 | -43304717625 |
| 25 | -148314737961 |
| 26 | -497033803314 |
| 27 | -1628721662260 |
| 28 | -5208556347700 |