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 | -15 |
| 3 | 141 |
| 4 | -1503 |
| 5 | 9117 |
| 6 | -46959 |
| 7 | 2349 |
| 8 | 1947969 |
| 9 | -26479299 |
| 10 | 166125105 |
| 11 | -476958771 |
| 12 | -7411008159 |
| 13 | 122517898461 |
| 14 | -1220344831791 |
| 15 | 7016585864301 |
| 16 | -14334148360575 |
| 17 | -334610402172291 |
| 18 | 4919241139007601 |
| 19 | -42532841711020275 |
| 20 | 172482611175249057 |
| 21 | 717799148664446493 |
| 22 | -24646866746992333551 |