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 | 2 |
| 3 | -3 |
| 4 | 5 |
| 5 | -9 |
| 6 | 18 |
| 7 | -39 |
| 8 | 88 |
| 9 | -200 |
| 10 | 449 |
| 11 | -988 |
| 12 | 2131 |
| 13 | -4527 |
| 14 | 9540 |
| 15 | -20090 |
| 16 | 42510 |
| 17 | -90596 |
| 18 | 194299 |
| 19 | -418105 |
| 20 | 899493 |
| 21 | -1929000 |
| 22 | 4116944 |
| 23 | -8742002 |
| 24 | 18484225 |
| 25 | -38974978 |
| 26 | 82086786 |
| 27 | -172927251 |
| 28 | 364700265 |
| 29 | -770223900 |
| 30 | 1628602725 |
| 31 | -3445907334 |
| 32 | 7291399538 |