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 | 0 |
| 2 | -2 |
| 3 | -3 |
| 4 | 8 |
| 5 | 40 |
| 6 | -20 |
| 7 | -651 |
| 8 | -1160 |
| 9 | 10872 |
| 10 | 53102 |
| 11 | -213235 |
| 12 | -2765684 |
| 13 | -4784988 |
| 14 | 42740178 |
| 15 | -433914495 |
| 16 | -15184673712 |
| 17 | -207885336400 |
| 18 | -2790244125426 |
| 19 | -48660847539651 |
| 20 | -950341379177012 |
| 21 | -18783035394110820 |