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 | -5 |
| 3 | 23 |
| 4 | 205 |
| 5 | -1681 |
| 6 | -22265 |
| 7 | 257543 |
| 8 | 4544185 |
| 9 | -67637281 |
| 10 | -1491632525 |
| 11 | 27138236663 |
| 12 | 718181418565 |
| 13 | -15442193173681 |
| 14 | -476768795646785 |
| 15 | 11828536957233383 |
| 16 | 417370516232719345 |
| 17 | -11735529528739490881 |
| 18 | -465849831125196593045 |
| 19 | 14639678925928297567703 |