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 | -9 |
| 2 | 54 |
| 3 | -324 |
| 4 | 1989 |
| 5 | -12204 |
| 6 | 74844 |
| 7 | -459072 |
| 8 | 2815830 |
| 9 | -17271468 |
| 10 | 105938118 |
| 11 | -649793448 |
| 12 | 3985642908 |
| 13 | -24446767374 |
| 14 | 149949318096 |
| 15 | -919745243064 |
| 16 | 5641448209173 |
| 17 | -34602992662356 |
| 18 | 212244632371188 |
| 19 | -1301846473509156 |
| 20 | 7985145356345268 |
| 21 | -48978545212087776 |