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 | -3 |
| 3 | 21 |
| 4 | -235 |
| 5 | 3630 |
| 6 | -71631 |
| 7 | 1721671 |
| 8 | -48804183 |
| 9 | 1594177605 |
| 10 | -58963348675 |
| 11 | 2435865852156 |
| 12 | -111169287046467 |
| 13 | 5554808694622369 |
| 14 | -301609325982387255 |
| 15 | 17682700497003095625 |
| 16 | -1113293610926803531951 |
| 17 | 74915504280675843548274 |
| 18 | -5365793673423031533999147 |