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 | 0 |
| 3 | -1 |
| 4 | -2 |
| 5 | -6 |
| 6 | -18 |
| 7 | -57 |
| 8 | -186 |
| 9 | -622 |
| 10 | -2120 |
| 11 | -7338 |
| 12 | -25724 |
| 13 | -91144 |
| 14 | -325878 |
| 15 | -1174281 |
| 16 | -4260282 |
| 17 | -15548694 |
| 18 | -57048048 |
| 19 | -210295326 |
| 20 | -778483932 |
| 21 | -2892818244 |
| 22 | -10786724388 |
| 23 | -40347919626 |
| 24 | -151355847012 |
| 25 | -569274150156 |