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 | 4 |
| 4 | -6 |
| 5 | 11 |
| 6 | -22 |
| 7 | 62 |
| 8 | -151 |
| 9 | 353 |
| 10 | -867 |
| 11 | 2261 |
| 12 | -5861 |
| 13 | 15178 |
| 14 | -39878 |
| 15 | 106099 |
| 16 | -283823 |
| 17 | 763248 |
| 18 | -2065453 |
| 19 | 5621318 |
| 20 | -15368682 |
| 21 | 42190539 |
| 22 | -116281176 |
| 23 | 321647511 |
| 24 | -892617214 |
| 25 | 2484583934 |
| 26 | -6935203356 |
| 27 | 19408586888 |
| 28 | -54447145335 |
| 29 | 153084848495 |