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 | 4 |
| 5 | 8 |
| 6 | 14 |
| 7 | 16 |
| 8 | -21 |
| 9 | -242 |
| 10 | -1166 |
| 11 | -4472 |
| 12 | -15132 |
| 13 | -46508 |
| 14 | -130016 |
| 15 | -323000 |
| 16 | -660535 |
| 17 | -786714 |
| 18 | 1789952 |
| 19 | 18546464 |
| 20 | 93845290 |
| 21 | 380532240 |
| 22 | 1355983860 |
| 23 | 4363436280 |
| 24 | 12688926510 |
| 25 | 32530717752 |
| 26 | 67666586472 |
| 27 | 76255301640 |
| 28 | -240266135872 |