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 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 2 |
| 6 | 9 |
| 7 | -6 |
| 8 | 118 |
| 9 | -568 |
| 10 | 4716 |
| 11 | -38160 |
| 12 | 358126 |
| 13 | -3662088 |
| 14 | 41073096 |
| 15 | -500013528 |
| 16 | 6573808200 |
| 17 | -92840971200 |
| 18 | 1402148010528 |
| 19 | -22554146644416 |
| 20 | 385014881294496 |
| 21 | -6952611764874240 |
| 22 | 132427188835260480 |
| 23 | -2653529921603890560 |
| 24 | 55802195178451990896 |