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 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 8 |
| 6 | 13 |
| 7 | -232 |
| 8 | -2199 |
| 9 | -25600 |
| 10 | -218311 |
| 11 | -2258048 |
| 12 | -20057555 |
| 13 | -212565376 |
| 14 | -1933691003 |
| 15 | -21159275264 |
| 16 | -181405779887 |
| 17 | -1935285600256 |
| 18 | -10159446470927 |
| 19 | -49976214294528 |
| 20 | 2835996855537109 |
| 21 | 63805712413261824 |