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) |
|---|---|
| 2 | 1 |
| 3 | -3 |
| 4 | 8 |
| 5 | -20 |
| 6 | 49 |
| 7 | -189 |
| 8 | 1791 |
| 9 | -21132 |
| 10 | 228306 |
| 11 | -2274690 |
| 12 | 22190772 |
| 13 | -230289696 |
| 14 | 2756380782 |
| 15 | -38757988710 |
| 16 | 608149754538 |
| 17 | -10057914084048 |
| 18 | 171037444641816 |
| 19 | -3000345245061048 |
| 20 | 55157102668064592 |
| 21 | -1077263181846230400 |
| 22 | 22411300073192730360 |
| 23 | -492846784406541548280 |