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 | 1 |
| 2 | 0 |
| 3 | -4 |
| 4 | -3 |
| 5 | 87 |
| 6 | 230 |
| 7 | -4583 |
| 8 | -27216 |
| 9 | 434928 |
| 10 | 4871719 |
| 11 | -62913079 |
| 12 | -1240374960 |
| 13 | 12230778601 |
| 14 | 426135019232 |
| 15 | -2759957884648 |
| 16 | -189393687667107 |
| 17 | 479371576805751 |
| 18 | 105233549909615798 |
| 19 | 233116575802412969 |
| 20 | -71022416772836562008 |
| 21 | -574100485456271792020 |