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 | 4 |
| 2 | 12 |
| 3 | 48 |
| 4 | 180 |
| 5 | 720 |
| 6 | 2832 |
| 7 | 11328 |
| 8 | 45132 |
| 9 | 180528 |
| 10 | 721392 |
| 11 | 2885568 |
| 12 | 11539440 |
| 13 | 46157760 |
| 14 | 184619712 |
| 15 | 738478848 |
| 16 | 2953870260 |
| 17 | 11815481040 |
| 18 | 47261743632 |
| 19 | 189046974528 |
| 20 | 756187176720 |
| 21 | 3024748706880 |
| 22 | 12098991941952 |