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 | 6 |
| 3 | 90 |
| 4 | 2520 |
| 5 | 113400 |
| 6 | 7484400 |
| 7 | 681080400 |
| 8 | 46118872800 |
| 9 | 2475822056400 |
| 10 | 113874710498640 |
| 11 | 4828589411913540 |