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 | 2 |
| 3 | 3 |
| 4 | 0 |
| 5 | -15 |
| 6 | -48 |
| 7 | -21 |
| 8 | 448 |
| 9 | 1953 |
| 10 | 640 |
| 11 | -32461 |
| 12 | -152064 |
| 13 | 77649 |
| 14 | 4331264 |
| 15 | 18557595 |
| 16 | -46686208 |
| 17 | -894805183 |
| 18 | -2948087808 |
| 19 | 21405607651 |
| 20 | 254321049600 |
| 21 | 421226202033 |
| 22 | -10904188190720 |
| 23 | -90171090228021 |
| 24 | 96102216892416 |
| 25 | 6418365899545825 |