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 | 6 |
| 3 | 18 |
| 4 | 90 |
| 5 | 192 |
| 6 | 864 |
| 7 | 1710 |
| 8 | 5970 |
| 9 | 13110 |
| 10 | 36810 |
| 11 | 75984 |
| 12 | 210546 |
| 13 | 410130 |
| 14 | 1003908 |
| 15 | 2045808 |
| 16 | 4616730 |
| 17 | 8950176 |
| 18 | 19746720 |
| 19 | 37297710 |
| 20 | 78247344 |
| 21 | 147410640 |
| 22 | 294299424 |
| 23 | 543058032 |
| 24 | 1067679540 |
| 25 | 1925323308 |
| 26 | 3653769792 |
| 27 | 6555529158 |
| 28 | 12129597486 |
| 29 | 21348640230 |