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) |
|---|---|
| 1 | 2 |
| 2 | 0 |
| 3 | 10 |
| 4 | 24 |
| 5 | 130 |
| 6 | 504 |
| 7 | 2210 |
| 8 | 9240 |
| 9 | 39338 |
| 10 | 166320 |
| 11 | 705058 |
| 12 | 2985840 |
| 13 | 12649570 |
| 14 | 53582256 |
| 15 | 226981610 |
| 16 | 961503816 |
| 17 | 4073004770 |
| 18 | 17253510120 |
| 19 | 73087065922 |
| 20 | 309601740360 |
| 21 | 1311494081482 |
| 22 | 5555577978720 |
| 23 | 23533806138050 |
| 24 | 99690802301664 |
| 25 | 422297015715650 |
| 26 | 1788878864564064 |
| 27 | 7577812474943050 |