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 | 1 |
| 3 | -1 |
| 4 | -7 |
| 5 | -16 |
| 6 | 19 |
| 7 | 270 |
| 8 | 809 |
| 9 | -1832 |
| 10 | -26939 |
| 11 | -81680 |
| 12 | 415817 |
| 13 | 5085192 |
| 14 | 11943199 |
| 15 | -154023064 |
| 16 | -1510744111 |
| 17 | -1192784896 |
| 18 | 80798373289 |
| 19 | 615743987520 |
| 20 | -1348945040647 |
| 21 | -55570193758592 |
| 22 | -296824726927253 |
| 23 | 2567750854163200 |
| 24 | 47111874571146041 |