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 | 1 |
| 4 | -23 |
| 5 | -119 |
| 6 | -359 |
| 7 | -839 |
| 8 | 78961 |
| 9 | 722737 |
| 10 | 3623761 |
| 11 | 13297681 |
| 12 | -2115602279 |
| 13 | -27917827079 |
| 14 | -195909017303 |
| 15 | -980236890359 |
| 16 | 219254440161121 |
| 17 | 3780662914771681 |
| 18 | 34105981790126881 |
| 19 | 216149350680413857 |
| 20 | -62275804867272039479 |
| 21 | -1325952502191492278039 |