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 | 2 |
| 4 | 3 |
| 5 | 14 |
| 6 | -55 |
| 7 | 62 |
| 8 | -637 |
| 9 | 338 |
| 10 | -3861 |
| 11 | 335312 |
| 12 | -4499803 |
| 13 | 43490108 |
| 14 | -246353731 |
| 15 | 2189950310 |
| 16 | -47336985225 |
| 17 | 1224524919590 |
| 18 | -21516426400621 |
| 19 | 346681988108648 |
| 20 | -4499477383730851 |
| 21 | 69294602646065900 |
| 22 | -1418045089870455795 |
| 23 | 45246859024830444566 |