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 | -6 |
| 3 | -21 |
| 4 | 286 |
| 5 | 1281 |
| 6 | -20592 |
| 7 | -100226 |
| 8 | 1749462 |
| 9 | 8899086 |
| 10 | -162993402 |
| 11 | -852079872 |
| 12 | 16106878320 |
| 13 | 85783258295 |
| 14 | -1658113447608 |
| 15 | -8950840125828 |
| 16 | 175904428301062 |
| 17 | 959332126312266 |
| 18 | -19096256882857668 |
| 19 | -104984591307499239 |
| 20 | 2111233112316364434 |