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 | 1 |
| 2 | 6 |
| 3 | 36 |
| 4 | 246 |
| 5 | 2046 |
| 6 | 19716 |
| 7 | 209616 |
| 8 | 2441916 |
| 9 | 31050396 |
| 10 | 425883816 |
| 11 | 6244077456 |
| 12 | 97391939976 |
| 13 | 1609040166696 |
| 14 | 28029696862896 |
| 15 | 512903202039936 |
| 16 | 9829166157390096 |
| 17 | 196739739722616336 |
| 18 | 4102788435212513376 |
| 19 | 88945209649582514496 |
| 20 | 2000700796384204930656 |