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 | 4 |
| 2 | 40 |
| 3 | 3280 |
| 4 | 21523360 |
| 5 | 926510094425920 |
| 6 | 1716841910146256242328924544640 |
| 7 | 5895092288869291585760436430706259332839105796137920554548480 |