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 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 6 |
| 6 | 28 |
| 7 | 126 |
| 8 | 520 |
| 9 | 2099 |
| 10 | 8429 |
| 11 | 33676 |
| 12 | 135201 |
| 13 | 543248 |
| 14 | 2195182 |
| 15 | 8893547 |
| 16 | 36196788 |
| 17 | 147739046 |
| 18 | 605138811 |
| 19 | 2485051070 |
| 20 | 10233284681 |
| 21 | 42234214910 |
| 22 | 174693725151 |