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 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 2 |
| 4 | 0 |
| 5 | 8 |
| 6 | -56 |
| 7 | 32 |
| 8 | 10176 |
| 9 | -215808 |
| 10 | -78784 |
| 11 | 150990912 |
| 12 | -3405688576 |
| 13 | -139041794560 |
| 14 | 10385778676736 |
| 15 | 130003936220160 |
| 16 | -43016304236761088 |
| 17 | 526545841919713280 |
| 18 | 266085261164348628992 |
| 19 | -12347306589339686547456 |