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 | 2 |
| 2 | 8 |
| 3 | 60 |
| 4 | 320 |
| 5 | 1980 |
| 6 | 10512 |
| 7 | 60788 |
| 8 | 320896 |
| 9 | 1787904 |
| 10 | 9381840 |
| 11 | 51081844 |
| 12 | 266680992 |
| 13 | 1429703548 |
| 14 | 7432424160 |
| 15 | 39409195740 |
| 16 | 204150606976 |
| 17 | 1073644675448 |
| 18 | 5545305620064 |
| 19 | 28980175671212 |
| 20 | 149302889205120 |