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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 24 |
| 5 | 70 |
| 6 | 180 |
| 7 | 434 |
| 8 | 1008 |
| 9 | 2286 |
| 10 | 5100 |
| 11 | 11242 |
| 12 | 24552 |
| 13 | 53222 |
| 14 | 114660 |
| 15 | 245730 |
| 16 | 524256 |
| 17 | 1114078 |
| 18 | 2359260 |
| 19 | 4980698 |
| 20 | 10485720 |
| 21 | 22020054 |
| 22 | 46137300 |
| 23 | 96468946 |
| 24 | 201326544 |
| 25 | 419430350 |
| 26 | 872415180 |
| 27 | 1811939274 |
| 28 | 3758096328 |
| 29 | 7784628166 |
| 30 | 16106127300 |
| 31 | 33285996482 |