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 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 119 |
| 6 | 709 |
| 7 | 4928 |
| 8 | 39144 |
| 9 | 349776 |
| 10 | 3472811 |
| 11 | 37928331 |
| 12 | 451891992 |
| 13 | 5832672456 |
| 14 | 81074690424 |
| 15 | 1207441809209 |
| 16 | 19181203110129 |
| 17 | 323753459184738 |
| 18 | 5785975294622694 |
| 19 | 109149016813544376 |
| 20 | 2167402030585724571 |
| 21 | 45190632809497874161 |
| 22 | 987099099863360190632 |