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 | 0 |
| 2 | 0 |
| 3 | 4 |
| 4 | 0 |
| 5 | 0 |
| 6 | -8 |
| 7 | 60 |
| 8 | -144 |
| 9 | 416 |
| 10 | -1248 |
| 11 | 4200 |
| 12 | -13248 |
| 13 | 42936 |
| 14 | -138072 |
| 15 | 452840 |
| 16 | -1480944 |
| 17 | 4883688 |
| 18 | -16114784 |
| 19 | 53457696 |
| 20 | -177637248 |