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 | -4 |
| 2 | 2 |
| 3 | 0 |
| 4 | -2 |
| 5 | -8 |
| 6 | -28 |
| 7 | -96 |
| 8 | -330 |
| 9 | -1144 |
| 10 | -4004 |
| 11 | -14144 |
| 12 | -50388 |
| 13 | -180880 |
| 14 | -653752 |
| 15 | -2377280 |
| 16 | -8691930 |
| 17 | -31935960 |
| 18 | -117858900 |
| 19 | -436698240 |
| 20 | -1623971580 |
| 21 | -6059188080 |
| 22 | -22676052360 |
| 23 | -85100059200 |
| 24 | -320188972740 |
| 25 | -1207569840048 |
| 26 | -4564276213608 |
| 27 | -17286920538496 |
| 28 | -65597689543400 |