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 | 3 |
| 2 | -1 |
| 3 | -26 |
| 4 | 29 |
| 5 | 756 |
| 6 | -1793 |
| 7 | -45744 |
| 8 | 189513 |
| 9 | 4700260 |
| 10 | -30515629 |
| 11 | -730341600 |
| 12 | 6948349069 |
| 13 | 159130156836 |
| 14 | -2123506814505 |
| 15 | -46081244842304 |
| 16 | 838034409016721 |
| 17 | 17029766318842692 |
| 18 | -414549408916313189 |
| 19 | -7774211453384941440 |
| 20 | 251026027696302116181 |
| 21 | 4263756050277024153028 |