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 | 4 |
| 5 | -7 |
| 6 | 21 |
| 7 | -51 |
| 8 | 113 |
| 9 | -498 |
| 10 | 1088 |
| 11 | -3335 |
| 12 | 21407 |
| 13 | -14653 |
| 14 | 232389 |
| 15 | -1275288 |
| 16 | -3636526 |
| 17 | -44468245 |
| 18 | -7468609 |
| 19 | 700603965 |
| 20 | 12178055777 |
| 21 | 67189448344 |
| 22 | 175549544778 |
| 23 | -2432123216941 |
| 24 | -36279392911507 |
| 25 | -287078642854853 |
| 26 | -945866835928323 |