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 | 9 |
| 5 | -23 |
| 6 | -25 |
| 7 | 583 |
| 8 | -3087 |
| 9 | 4401 |
| 10 | 79087 |
| 11 | -902097 |
| 12 | 4783801 |
| 13 | 2361049 |
| 14 | -348382697 |
| 15 | 4102879415 |
| 16 | -24288551071 |
| 17 | -47413121055 |
| 18 | 3214104039007 |
| 19 | -44472852461857 |
| 20 | 326386562502889 |
| 21 | 417716032223049 |
| 22 | -55104307651136313 |
| 23 | 962111031220099495 |