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 | 0 |
| 2 | -1 |
| 3 | -4 |
| 4 | -12 |
| 5 | -33 |
| 6 | -88 |
| 7 | -232 |
| 8 | -609 |
| 9 | -1596 |
| 10 | -4180 |
| 11 | -10945 |
| 12 | -28656 |
| 13 | -75024 |
| 14 | -196417 |
| 15 | -514228 |
| 16 | -1346268 |
| 17 | -3524577 |
| 18 | -9227464 |
| 19 | -24157816 |
| 20 | -63245985 |
| 21 | -165580140 |
| 22 | -433494436 |
| 23 | -1134903169 |
| 24 | -2971215072 |
| 25 | -7778742048 |
| 26 | -20365011073 |
| 27 | -53316291172 |
| 28 | -139583862444 |