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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 3 |
| 5 | 7 |
| 6 | -23 |
| 7 | -73 |
| 8 | -57 |
| 9 | 186 |
| 10 | 2126 |
| 11 | 3161 |
| 12 | 3885 |
| 13 | 12731 |
| 14 | 39462 |
| 15 | -13815 |
| 16 | -151907 |
| 17 | 1117163 |
| 18 | 5045162 |
| 19 | -19274680 |
| 20 | 18700047 |
| 21 | 127912738 |
| 22 | 252060543 |
| 23 | -656184524 |
| 24 | 2799754423 |
| 25 | 5292148929 |
| 26 | 27646015077 |
| 27 | 49454963317 |
| 28 | 271968742992 |