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 | 0 |
| 1 | 0 |
| 2 | 18 |
| 3 | 162 |
| 4 | 972 |
| 5 | 4860 |
| 6 | 21870 |
| 7 | 91854 |
| 8 | 367416 |
| 9 | 1417176 |
| 10 | 5314410 |
| 11 | 19486170 |
| 12 | 70150212 |
| 13 | 248714388 |
| 14 | 870500358 |
| 15 | 3013270470 |
| 16 | 10331213040 |
| 17 | 35126124336 |
| 18 | 118550669634 |
| 19 | 397493421714 |
| 20 | 1324978072380 |
| 21 | 4393348345260 |
| 22 | 14498049539358 |