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 | 0 |
| 2 | 2 |
| 3 | 4 |
| 4 | 14 |
| 5 | 40 |
| 6 | 132 |
| 7 | 424 |
| 8 | 1430 |
| 9 | 4848 |
| 10 | 16796 |
| 11 | 58744 |
| 12 | 208012 |
| 13 | 742768 |
| 14 | 2674440 |
| 15 | 9694416 |
| 16 | 35357670 |
| 17 | 129643360 |
| 18 | 477638700 |
| 19 | 1767258328 |
| 20 | 6564120420 |
| 21 | 24466250224 |
| 22 | 91482563640 |
| 23 | 343059554864 |
| 24 | 1289904147324 |
| 25 | 4861946193440 |
| 26 | 18367353072152 |