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 | 2 |
| 1 | 1 |
| 2 | 0 |
| 3 | 2 |
| 4 | 6 |
| 5 | 16 |
| 6 | 60 |
| 7 | 272 |
| 8 | 1386 |
| 9 | 7936 |
| 10 | 50520 |
| 11 | 353792 |
| 12 | 2702766 |
| 13 | 22368256 |
| 14 | 199360980 |
| 15 | 1903757312 |
| 16 | 19391512146 |
| 17 | 209865342976 |
| 18 | 2404879675440 |
| 19 | 29088885112832 |
| 20 | 370371188237526 |
| 21 | 4951498053124096 |
| 22 | 69348874393137900 |