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 | 6 |
| 3 | 28 |
| 4 | 220 |
| 5 | 2565 |
| 6 | 45846 |
| 7 | 1268622 |
| 8 | 55336336 |
| 9 | 3876385680 |
| 10 | 443603651136 |
| 11 | 84205632289664 |