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 | 0 |
| 2 | 1 |
| 3 | 0 |
| 4 | -1 |
| 5 | 5 |
| 6 | -14 |
| 7 | 35 |
| 8 | -81 |
| 9 | 180 |
| 10 | -389 |
| 11 | 825 |
| 12 | -1726 |
| 13 | 3575 |
| 14 | -7349 |
| 15 | 15020 |
| 16 | -30561 |
| 17 | 61965 |
| 18 | -125294 |
| 19 | 252795 |
| 20 | -509161 |
| 21 | 1024100 |
| 22 | -2057549 |
| 23 | 4130225 |
| 24 | -8284926 |
| 25 | 16609455 |
| 26 | -33282989 |
| 27 | 66669660 |
| 28 | -133507081 |
| 29 | 267285605 |
| 30 | -535010414 |
| 31 | 1070731475 |
| 32 | -2142612801 |
| 33 | 4287086100 |