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 | 17 |
| 3 | -145 |
| 4 | 1313 |
| 5 | -11809 |
| 6 | 106289 |
| 7 | -956593 |
| 8 | 8609345 |
| 9 | -77484097 |
| 10 | 697356881 |
| 11 | -6276211921 |
| 12 | 56485907297 |
| 13 | -508373165665 |
| 14 | 4575358490993 |
| 15 | -41178226418929 |
| 16 | 370604037770369 |
| 17 | -3335436339933313 |
| 18 | 30018927059399825 |
| 19 | -270170343534598417 |
| 20 | 2431533091811385761 |