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 | -3 |
| 3 | 20 |
| 4 | -189 |
| 5 | 2232 |
| 6 | -31130 |
| 7 | 497016 |
| 8 | -8907885 |
| 9 | 176829104 |
| 10 | -3849436062 |
| 11 | 91187523000 |
| 12 | -2335691914050 |
| 13 | 64344487654800 |
| 14 | -1897619527612692 |
| 15 | 59667237154623280 |
| 16 | -1993022006345620605 |
| 17 | 70488571028815935072 |
| 18 | -2631925423768158446390 |