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 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 12 |
| 5 | 36 |
| 6 | 156 |
| 7 | 544 |
| 8 | 2144 |
| 9 | 7872 |
| 10 | 30096 |
| 11 | 112416 |
| 12 | 425536 |
| 13 | 1598528 |
| 14 | 6031296 |
| 15 | 22699008 |
| 16 | 85552128 |
| 17 | 322177024 |
| 18 | 1213849856 |
| 19 | 4572111360 |
| 20 | 17224104960 |
| 21 | 64880993280 |
| 22 | 244410981376 |
| 23 | 920685043712 |
| 24 | 3468237545472 |
| 25 | 13064787542016 |