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 | 2 |
| 2 | 12 |
| 3 | 40 |
| 4 | 252 |
| 5 | 880 |
| 6 | 10880 |
| 7 | 75852 |
| 8 | 715816960 |
| 9 | 62549517598720 |