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 | 2 |
| 2 | -3 |
| 3 | 12 |
| 4 | -58 |
| 5 | 312 |
| 6 | -1794 |
| 7 | 10794 |
| 8 | -67113 |
| 9 | 427800 |
| 10 | -2780677 |
| 11 | 18360504 |
| 12 | -122809416 |
| 13 | 830379966 |
| 14 | -5666465445 |
| 15 | 38974338126 |
| 16 | -269915089194 |
| 17 | 1880576960904 |
| 18 | -13172489198859 |
| 19 | 92705253700620 |
| 20 | -655219698720486 |
| 21 | 4648722344211012 |
| 22 | -33096948925057703 |