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 | 3 |
| 3 | -5 |
| 4 | 17 |
| 5 | -31 |
| 6 | 119 |
| 7 | -211 |
| 8 | 937 |
| 9 | -1483 |
| 10 | 8015 |
| 11 | -10187 |
| 12 | 73369 |
| 13 | -62193 |
| 14 | 713907 |
| 15 | -234857 |
| 16 | 7358657 |
| 17 | 1881661 |
| 18 | 80117735 |
| 19 | 69295469 |
| 20 | 917837521 |
| 21 | 1334044075 |
| 22 | 11006114883 |
| 23 | 21830065899 |
| 24 | 137275956089 |
| 25 | 333858963899 |
| 26 | 1769128762419 |
| 27 | 4940496514271 |
| 28 | 23409778504937 |