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 | -1 |
| 3 | 4 |
| 4 | -21 |
| 5 | 110 |
| 6 | -616 |
| 7 | 3738 |
| 8 | -23619 |
| 9 | 152470 |
| 10 | -1003776 |
| 11 | 6726702 |
| 12 | -45720504 |
| 13 | 314307018 |
| 14 | -2181641134 |
| 15 | 15269811260 |
| 16 | -107651952999 |
| 17 | 763745165826 |
| 18 | -5448656285938 |
| 19 | 39063995033178 |
| 20 | -281309141648214 |
| 21 | 2033846965665156 |
| 22 | -14757571862304042 |
| 23 | 107431429198117338 |
| 24 | -784411267743868602 |
| 25 | 5743068864740600214 |