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 | 5 |
| 4 | -3 |
| 5 | -21 |
| 6 | 51 |
| 7 | 41 |
| 8 | -391 |
| 9 | 407 |
| 10 | 1927 |
| 11 | -6227 |
| 12 | -2507 |
| 13 | 49347 |
| 14 | -71109 |
| 15 | -236079 |
| 16 | 966129 |
| 17 | 9519 |
| 18 | -7408497 |
| 19 | 13685205 |
| 20 | 32079981 |
| 21 | -167077221 |
| 22 | 60639939 |
| 23 | 1209248505 |
| 24 | -2761755543 |
| 25 | -4457338681 |
| 26 | 30629783831 |
| 27 | -22124857219 |
| 28 | -206064020315 |
| 29 | 572040039283 |
| 30 | 590258340811 |