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 | 6 |
| 4 | -52 |
| 5 | 540 |
| 6 | -7608 |
| 7 | 129304 |
| 8 | -2612608 |
| 9 | 60867360 |
| 10 | -1608663840 |
| 11 | 47527158624 |
| 12 | -1552431588288 |
| 13 | 55547889458880 |
| 14 | -2160724031160576 |
| 15 | 90782738645280000 |
| 16 | -4097139872604807168 |
| 17 | 197675862365363088384 |
| 18 | -10153243488783257091072 |