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 | 9 |
| 3 | -16 |
| 4 | 65 |
| 5 | -160 |
| 6 | 465 |
| 7 | -1216 |
| 8 | 3273 |
| 9 | -8608 |
| 10 | 22721 |
| 11 | -59648 |
| 12 | 156577 |
| 13 | -410432 |
| 14 | 1075529 |
| 15 | -2817200 |
| 16 | 7378049 |
| 17 | -19319840 |
| 18 | 50586481 |
| 19 | -132447360 |
| 20 | 346768521 |
| 21 | -907878720 |
| 22 | 2376901249 |
| 23 | -6222878976 |
| 24 | 16291823425 |
| 25 | -42652732800 |
| 26 | 111666604425 |
| 27 | -292347451216 |
| 28 | 765376349633 |
| 29 | -2003782568608 |