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 | 1 |
| 3 | 2 |
| 4 | -1 |
| 5 | -3 |
| 6 | -5 |
| 7 | 8 |
| 8 | -19 |
| 9 | 87 |
| 10 | 715 |
| 11 | -13672 |
| 12 | -1190179 |
| 13 | -850964313 |
| 14 | 11634385277515 |
| 15 | -13847001034356560872 |
| 16 | 11783303722311508585098883421 |
| 17 | 137091495347348713307137824784782074139687 |
| 18 | -1898306077876225285447341619480271058010077969630158545410485 |