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) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | -1 |
| 4 | 3 |
| 5 | -8 |
| 6 | 21 |
| 7 | -54 |
| 8 | 134 |
| 9 | -318 |
| 10 | 720 |
| 11 | -1560 |
| 12 | 3259 |
| 13 | -6641 |
| 14 | 13391 |
| 15 | -27107 |
| 16 | 55657 |
| 17 | -116244 |
| 18 | 245823 |
| 19 | -521738 |
| 20 | 1101566 |
| 21 | -2299215 |
| 22 | 4730990 |
| 23 | -9601095 |
| 24 | 19273729 |
| 25 | -38446742 |
| 26 | 76598275 |
| 27 | -153119606 |
| 28 | 308061214 |
| 29 | -624460449 |
| 30 | 1274268038 |
| 31 | -2611866713 |
| 32 | 5362888620 |
| 33 | -11003127203 |
| 34 | 22516189988 |