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 | -1 |
| 3 | 1 |
| 4 | -1 |
| 5 | 0 |
| 6 | 5 |
| 7 | -18 |
| 8 | 27 |
| 9 | 67 |
| 10 | -496 |
| 11 | 496 |
| 12 | 6963 |
| 13 | -24246 |
| 14 | -148002 |
| 15 | 1138045 |
| 16 | 3360042 |
| 17 | -58828040 |
| 18 | -33243252 |
| 19 | 3312139446 |
| 20 | -5235582541 |
| 21 | -204462055464 |
| 22 | 726496668085 |
| 23 | 14922365946662 |
| 24 | -84161948692035 |
| 25 | -1310383972147810 |