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 | -12 |
| 4 | 144 |
| 5 | 2400 |
| 6 | -28224 |
| 7 | -1296000 |
| 8 | 50808384 |
| 9 | 2434614000 |
| 10 | -85975622656 |
| 11 | -8396400230400 |
| 12 | 691198592910336 |
| 13 | 65694715632000000 |
| 14 | -4784543769600000000 |
| 15 | -796566295447796966400 |
| 16 | 112616674749446400000000 |
| 17 | 17805426854398997299200000 |
| 18 | -2223594618178251399873232896 |