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 | 4 |
| 3 | 27 |
| 4 | 240 |
| 5 | 2345 |
| 6 | 17280 |
| 7 | -226597 |
| 8 | -21007616 |
| 9 | -1007159823 |
| 10 | -42976972800 |
| 11 | -1775328986981 |
| 12 | -72123329507328 |
| 13 | -2843431148886887 |
| 14 | -103621659777126400 |
| 15 | -2971936506262036965 |
| 16 | -6719764584265482240 |
| 17 | 9528526268302653725537 |
| 18 | 1192610999728818101551104 |