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 | -2 |
| 3 | 9 |
| 4 | -28 |
| 5 | 185 |
| 6 | -846 |
| 7 | 7777 |
| 8 | -47384 |
| 9 | 559953 |
| 10 | -4264570 |
| 11 | 61594841 |
| 12 | -562923252 |
| 13 | 9608795209 |
| 14 | -102452031878 |
| 15 | 2017846993905 |
| 16 | -24588487650736 |
| 17 | 548854382342177 |
| 18 | -7524077221125234 |
| 19 | 187708198761024553 |
| 20 | -2859149344027588940 |
| 21 | 78837443479630312281 |
| 22 | -1320926996940746090302 |