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 | -4 |
| 2 | 61 |
| 3 | -55 |
| 4 | 14909 |
| 5 | -2365 |
| 6 | 791251 |
| 7 | -81235 |
| 8 | 18611189 |
| 9 | -2688697 |
| 10 | 1314206255 |
| 11 | -75360175 |
| 12 | 1474324903679 |
| 13 | -3120712309 |
| 14 | 148245882757 |
| 15 | 73095622325 |
| 16 | -601280097848267 |
| 17 | -37106070169201 |
| 18 | 382216911865193617 |
| 19 | 10910986778031065 |
| 20 | -53074470254129087681 |
| 21 | -4201158650597043373 |