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 | 2 |
| 3 | -17 |
| 4 | 124 |
| 5 | -2764 |
| 6 | 43688 |
| 7 | -1859138 |
| 8 | 51236656 |
| 9 | -3550889296 |
| 10 | 151107728672 |
| 11 | -15494138893232 |
| 12 | 941930695305664 |
| 13 | -133994296272170944 |
| 14 | 11024086088089751168 |
| 15 | -2077570618897716831248 |
| 16 | 222290021402867410844416 |
| 17 | -53603997631397508980982016 |
| 18 | 7234385689981722178901729792 |