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 | 3 |
| 3 | -7 |
| 4 | 17 |
| 5 | -41 |
| 6 | 99 |
| 7 | -239 |
| 8 | 577 |
| 9 | -1393 |
| 10 | 3363 |
| 11 | -8119 |
| 12 | 19601 |
| 13 | -47321 |
| 14 | 114243 |
| 15 | -275807 |
| 16 | 665857 |
| 17 | -1607521 |
| 18 | 3880899 |
| 19 | -9369319 |
| 20 | 22619537 |
| 21 | -54608393 |
| 22 | 131836323 |
| 23 | -318281039 |
| 24 | 768398401 |
| 25 | -1855077841 |
| 26 | 4478554083 |
| 27 | -10812186007 |
| 28 | 26102926097 |
| 29 | -63018038201 |
| 30 | 152139002499 |