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 | 1 |
| 3 | -2 |
| 4 | -11 |
| 5 | 8 |
| 6 | 253 |
| 7 | 344 |
| 8 | -9463 |
| 9 | -44416 |
| 10 | 491609 |
| 11 | 5130368 |
| 12 | -30257347 |
| 13 | -688030080 |
| 14 | 1480493589 |
| 15 | 109875416832 |
| 16 | 177416283793 |
| 17 | -20650894622720 |
| 18 | -125705754161615 |
| 19 | 4460981432725504 |
| 20 | 53738108098148101 |
| 21 | -1069938200055119872 |