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 | 2 |
| 2 | -6 |
| 3 | 32 |
| 4 | -210 |
| 5 | 1536 |
| 6 | -12012 |
| 7 | 98304 |
| 8 | -831402 |
| 9 | 7208960 |
| 10 | -63740820 |
| 11 | 572522496 |
| 12 | -5209363380 |
| 13 | 47915728896 |
| 14 | -444799488600 |
| 15 | 4161823309824 |
| 16 | -39209074920090 |
| 17 | 371626340253696 |
| 18 | -3541117629057540 |
| 19 | 33902753847705600 |
| 20 | -325969196485349340 |
| 21 | 3146175557067079680 |
| 22 | -30471769822097981160 |