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 | -2 |
| 2 | 5 |
| 3 | -17 |
| 4 | 79 |
| 5 | -471 |
| 6 | 3391 |
| 7 | -28451 |
| 8 | 272447 |
| 9 | -2933807 |
| 10 | 35102403 |
| 11 | -462021525 |
| 12 | 6634207777 |
| 13 | -103200019093 |
| 14 | 1728836723813 |
| 15 | -31030630439249 |
| 16 | 594094812208133 |
| 17 | -12085090282079299 |
| 18 | 260296103744105623 |
| 19 | -5917885334682695549 |
| 20 | 141625618336446419151 |