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 | 1 |
| 4 | -1 |
| 5 | 3 |
| 6 | -4 |
| 7 | 10 |
| 8 | -20 |
| 9 | 42 |
| 10 | -98 |
| 11 | 210 |
| 12 | -492 |
| 13 | 1122 |
| 14 | -2607 |
| 15 | 6149 |
| 16 | -14443 |
| 17 | 34463 |
| 18 | -82238 |
| 19 | 197574 |
| 20 | -476918 |
| 21 | 1154402 |
| 22 | -2807516 |
| 23 | 6845016 |
| 24 | -16743674 |
| 25 | 41067512 |
| 26 | -100967539 |
| 27 | 248843095 |
| 28 | -614546545 |
| 29 | 1520779665 |