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 | 0 |
| 2 | -3 |
| 3 | 5 |
| 4 | 29 |
| 5 | -181 |
| 6 | -401 |
| 7 | 9645 |
| 8 | -14183 |
| 9 | -689257 |
| 10 | 4826171 |
| 11 | 55700633 |
| 12 | -1024570955 |
| 13 | -2770525005 |
| 14 | 221566919911 |
| 15 | -1028838834811 |
| 16 | -49439771820367 |
| 17 | 723165789334703 |
| 18 | 9903852025111027 |
| 19 | -362150510124039471 |
| 20 | -463774017017434739 |
| 21 | 169793689786411161995 |