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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | -4 |
| 6 | 96 |
| 7 | -48 |
| 8 | -384 |
| 9 | -3456 |
| 10 | 328320 |
| 11 | -17280 |
| 12 | -207360 |
| 13 | -481697280 |
| 14 | -516741120 |
| 15 | 79427174400 |
| 16 | 1270834790400 |
| 17 | 681401548800 |
| 18 | 12265227878400 |
| 19 | -6169334376038400 |
| 20 | -123386687520768000 |
| 21 | -158218429759488000 |
| 22 | 47610136717000704000 |