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) |
|---|---|
| 2 | -6 |
| 3 | -79 |
| 4 | -515 |
| 5 | -2255 |
| 6 | -7321 |
| 7 | -17280 |
| 8 | -20052 |
| 9 | 73530 |
| 10 | 683280 |
| 11 | 3482667 |
| 12 | 14574887 |
| 13 | 55023247 |
| 14 | 194872885 |
| 15 | 661036370 |
| 16 | 2174736558 |
| 17 | 6996176016 |
| 18 | 22133771190 |
| 19 | 69145507605 |
| 20 | 213941135265 |
| 21 | 657095902685 |