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 | -4 |
| 4 | 16 |
| 5 | -69 |
| 6 | 371 |
| 7 | -2719 |
| 8 | 24691 |
| 9 | -243804 |
| 10 | 2479276 |
| 11 | -25931249 |
| 12 | 284075601 |
| 13 | -3320433179 |
| 14 | 41744590941 |
| 15 | -561939568544 |
| 16 | 8008026088996 |
| 17 | -119496752915869 |
| 18 | 1854697111334891 |
| 19 | -29870689367146379 |
| 20 | 499291484226079551 |
| 21 | -8668202648905259624 |
| 22 | 156301404533216141576 |