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 | -19 |
| 5 | -75 |
| 6 | -260 |
| 7 | -464 |
| 8 | 5745 |
| 9 | 118145 |
| 10 | 1638416 |
| 11 | 20803836 |
| 12 | 258490285 |
| 13 | 3203144581 |
| 14 | 39595146396 |
| 15 | 481418955200 |
| 16 | 5547932810945 |
| 17 | 54569481140961 |
| 18 | 257079620051200 |
| 19 | -8335537038105380 |
| 20 | -407961130194651699 |