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 | -4 |
| 3 | 9 |
| 4 | 64 |
| 5 | -225 |
| 6 | -2304 |
| 7 | 11025 |
| 8 | 147456 |
| 9 | -893025 |
| 10 | -14745600 |
| 11 | 108056025 |
| 12 | 2123366400 |
| 13 | -18261468225 |
| 14 | -416179814400 |
| 15 | 4108830350625 |
| 16 | 106542032486400 |
| 17 | -1187451971330625 |
| 18 | -34519618525593600 |
| 19 | 428670161650355625 |
| 20 | 13807847410237440000 |
| 21 | -189043541287806830625 |
| 22 | -6682998146554920960000 |