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 | -2 |
| 4 | 6 |
| 5 | -22 |
| 6 | 80 |
| 7 | -228 |
| 8 | 18 |
| 9 | 6694 |
| 10 | -65604 |
| 11 | 396804 |
| 12 | -1336332 |
| 13 | -2510244 |
| 14 | 64799884 |
| 15 | -302351144 |
| 16 | -1410221598 |
| 17 | 23754923526 |
| 18 | 16833211660 |
| 19 | -2598949277964 |
| 20 | 14767224078420 |
| 21 | 229529725999500 |
| 22 | -3478598282993328 |
| 23 | -13287810766972728 |
| 24 | 667271251276705140 |
| 25 | -1630867775606147844 |