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 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 9 |
| 4 | -16 |
| 5 | 105 |
| 6 | -336 |
| 7 | 1513 |
| 8 | -5712 |
| 9 | 23529 |
| 10 | -92752 |
| 11 | 373737 |
| 12 | -1489488 |
| 13 | 5968873 |
| 14 | -23853648 |
| 15 | 95458281 |
| 16 | -381745744 |
| 17 | 1527157737 |
| 18 | -6108281424 |
| 19 | 24433824745 |
| 20 | -97733900880 |
| 21 | 390938399721 |
| 22 | -1563748006480 |