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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 1 |
| 5 | -7 |
| 6 | -16 |
| 7 | -57 |
| 8 | -113 |
| 9 | 670 |
| 10 | 3983 |
| 11 | 23647 |
| 12 | 140576 |
| 13 | -833503 |
| 14 | -14871471 |
| 15 | -147165662 |
| 16 | -2273917871 |
| 17 | 11396432249 |
| 18 | 808162720720 |
| 19 | 14252325989831 |
| 20 | 503020937289311 |
| 21 | 23268424032702 |
| 22 | -625775582778294689 |
| 23 | -22086170583356766977 |
| 24 | -1557994930804790259136 |
| 25 | -27620103680757212617727 |
| 26 | 6783061219100782906098017 |
| 27 | 547569584492952570186575810 |