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 | -4 |
| 3 | 19 |
| 4 | -100 |
| 5 | 569 |
| 6 | -3416 |
| 7 | 21302 |
| 8 | -136636 |
| 9 | 895572 |
| 10 | -5971096 |
| 11 | 40366463 |
| 12 | -276036720 |
| 13 | 1905940182 |
| 14 | -13269019988 |
| 15 | 93040431283 |
| 16 | -656472509864 |
| 17 | 4657492107245 |
| 18 | -33205607204468 |
| 19 | 237777067846451 |
| 20 | -1709374453370956 |
| 21 | 12332468208675821 |
| 22 | -89262196983781332 |
| 23 | 647988910138661556 |