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 | 4 |
| 3 | -18 |
| 4 | 128 |
| 5 | -1375 |
| 6 | 19224 |
| 7 | -328937 |
| 8 | 6594560 |
| 9 | -150804585 |
| 10 | 3866510000 |
| 11 | -109763181693 |
| 12 | 3416538258432 |
| 13 | -115680589167780 |
| 14 | 4232540747232224 |
| 15 | -166402907912306250 |
| 16 | 6995675389431382016 |
| 17 | -313160900844718102493 |
| 18 | 14871520058618111804352 |
| 19 | -746718033885917073001959 |