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 | 1 |
| 3 | 3 |
| 4 | 6 |
| 5 | 390 |
| 6 | 13860 |
| 7 | 23892750 |
| 8 | 80215013340 |
| 9 | 9851050382488595280 |
| 10 | 694858921540030774800 |
| 11 | 344551675909308833470705200 |
| 12 | 1955049249155875335764556836119978483886656454640 |